Thank you for your comment, Ziggy!
Thats a very valid point you are making! 
Maybe I can find that video, check it out and integrate his advice into my practise!
Here is a current attempt on shading som spheres! I really like the quality jump from sphere 1-3 to 4-10. When I started with #4, I decided to take more time with each one of them. Working slower and really taking the time to do things seems to be a reoccurring pattern in my practises. I might have subconsciously increased my tempo by watching youtube artists as all their works are obviously sped up to fit a 10-20min video...
Well whatever, here's today's practise
I can definitely see the improvement with your later spheres! I love the ones you did with the back lighting. The build up of values is really subtle and looks really nice.
One thing I notice with most of these is the transition between the core shadow and lit area of the sphere is too abrupt. It almost looks like the sphere is two different colors/shades. I think it would help to add more values to make the transition smoother. I think number 5 does this really well. Also, don't be afraid to go stronger and lighter on the bounce light.
This depends on what style you want, but I think going over them with a low opacity soft brush will give them more of a finished look.
Hope this helps!
Oh yeah that makes a lot of sense, Lesley! I might have misunderstood sth regarding bounce light: You sure know about the rule that "the darkes light ist lighter than the lightest dark." --> does this also apply to the bounce light? Because I think the main reason why my bounce lights are so light is because I was kinda afraid to break that rule...
Also thank you so much, Lesley for always taking so much time to give feedback and to provide in such graphic and easy to understand way! 
Of course, I'm always happy to help!
In general I think that rule is good to follow when doings that are from imagination like this. I think there are rare cases where this isn't true, but I think it is when it comes to bounce light. I eye dropped values from shapes and the bounce light was darker than any value on the lit side. One comes close, but it's still slightly darker. 
You bring up a good point with your sphere though. I think for 10 I'd say it's good to go lighter on the bounce light, but for 8 and 3 it's better to make the core shadow darker instead. I should've mentioned that I had to use a darker value for them.
Here's today's practise. I think the spheres with lighter base value still look kinda wrong, but I am pretty happy with the darker ones! (like the first and last of the second row )
Also tried to lighten the bounce lights, but I am not where I want to be yet...
Have a great day everyone!
And in addition to that I am currently working on a "personal" piece where I tried to implement what I am currently learning into sth more creative.
So I thought where would I be able to draw a lot of spheres? Okay yeah, a billiard table. But I wanted the balls to be lit from different angles, so I though: the solar system! Nice slap some bounce light on, bcs that stuff apparently doesnt exist in outer space (because science ) so I ended up with an orrery!
Here's the current progress. I am not yet sure if all balls are correctly shaded, so I'd be very happy about some quick feedback from your end, everyone! 
This looks really cool and believable!
I'd say go darker on the shadows and blend more in the middle so it doesn't jump too sudden from dark to light.
Can't wait to see this finished.
Thank you for the feedback Lesley!
Here is the new version:
I don't quite know how to go on with this piece. I guess I have to make up my mind first about what is actually around the Orrery in order to do stuff like bounce lights and also attempting to render the materials.
Maybe I should phrase my question like that: When I have practised the stuff I intended to practise with a practise piece, should I keep going (even though that would mean "wasting" a lot of time with other things like rendering materials), or should I call it a day and go on to the next practise piece?
Have a great weekend, everyone! 
Unless you want to study materials I would just move on until you get to the material section of the course.
If it were me I'd go back to portraits and start learning how to apply the blending techniques to the face. Correct me if I'm wrong but didn't you start doing shading and value studies a month ago to start rendering the face? I would start trying to shade each facial feature and do mini challenges like 5 a day or something. Or you could try lighting the Asaro head based on moods like "dramatic" or "lonely" etc to make it interesting. You've made a lot of progress with shading but outside looking in it seems like you're diving into a tangent since you started off wanting to shade better but now you're considering rending materials.
Haha you are definetly right, Lesley, I am getting a little distracted with the value studies
I actually started working on shading the human nose (along with Istebraks tutorial), but I also started my new job this monday and I am still struggling with gathering the concentration to do my art practise I hope I'll adapt soon, so I can push further.
Until then, I'll keep doing the form studies as they have become a little easier by now...
Thank you so much for your comment!
Here is today's practise session. I am not really sure how to really practise shading the nose. It seems so complex and working from foto reference is quite tough as all the shading is so soft 
How do you practise shading/constructing facial features?
I are you going for an exact replica? These look a lot darker than the references.
Just asking so I can give better feedback.
I just used them to construct the nose itself and then I tried to do my own light setup like in my form studies.
I just wanted to get something done last week, work has been really tedious and I couldnt concentrate.
Ah okay, that makes sense.
For me I usually study everything as it is so I can understand the forms and nuances for the feature. Then I'll do one or two on my own to see if I can make it fit with the others.
I think what you're doing is good practice too. It may be helpful to do one or two just like the reference to get a better idea of the plane changes and then change the lighting for a few others. On the ones you did, the the wings of the nose aren't as defined and the shapes are a little off. I think you did well with choosing the the correct values.
I just noticed this, but have you done any organic form studies? It might help to do those as a warm up since facial features are more organic.
Hope this helps!
Thank you for the feedback, Lesley. Apart from the spheres, I haven't done any organic form studies yet, but good point, I'll go to do those first and then continue on with facial features. Maybe that ends up being a little less frustrating
Did another form study today mixing in organic and geometric forms. Organic forms are really tough as I feel like I still lack the brushmanship with the soft brush, its super hard to control it and i often end up with hard edges which I have to soften with the smudge tool afterwards.
Also still a little unsure about my values in general. Often the core shadow of an object appears as if it had a totally different base color 
And here is today's form study. Took about 2.5-3 hours
I especially enjoyed adding the cracks and details in the end
There is one question I have: I noticed in the bottom right form I have a very strong bounce light coming from the plane where the cast shadow lands. Is it even possible to have bounce light from a plane that has a drop shadow on it? 
I wish you all a great weekend!
Here is todays organic form study.
Way better than last time, I still have a lot of things to work on 
Have a great day everyone
You got some nice blending between the values. These are really looking wonderful. Keep it up!
Thank you so much for the kind words, @afoster1138!
Here is today's practise:
Have a great day, everyone!
