well, for planning I would say, assign ( I assume out of the 74 days) the next 4-5 days max. to creating the concept or atleast the idea, so you know what kind of thing/being you will be making. every ''theme'' has general kit pieces, for example: my robot has a lot of robotic things, I do not know what the final design is, and am just blocking things out in seperate meshes so I can re-use them aka modula(i)r design. very handy. but I do still advice spending some time maybe talking with people about an idea you have, maybe you didn't see things like they did or they give you that small ''eureka'' spark and you have an idea! then spend the next following days fleshing it out a bit more, like blocking stuff out, drawing silhouetes (very important ) to get a feel for it. this is not an exact science, so if something doesn't look right in a character but looks cool/interesting you will probally get away with it.
for some turorials you want to follow, for hard surface in 2d/3d and maybe even other kinds of designs I recommend this one: https://cubebrush.co/jpdesign?product_id=wlfu6a
It goes into the thought process of simplyfing complex shapes by dividing them in bigger and simple shapes, gives you a lot of examples and also it really helped me in designing some things. also, this week up until saturday there is that sale Cubebrush is having, (on the front page it tells you what the coupon code is, in that green banner.) gives you 20% off on all products so, if you were thinking about it, strike while the iron is hot!
but, lets continue. after having a concept of your champion/character I would say, block it out in rough and simpel shapes in your 3d software now, use shapes such as cylinders and boxes maybe a sphere too. and see how the silhouete feels. and do share that with us, see what might be beter or could be improved upon further, you know, bring out that sweet characteristic of a character. that is what gives it a personality probally.
anyway! after having all that done and probally having spend 10-15 days ( I am taking big time slots since you could get stuck somewhere or have a art block (god forbid)) you now have a idea of what you want to make and this should speed up your proces, since you now have a goal of what you want exactly. very important you do not want to lose interest before this stage because than it will end up in our ''never to see the light of day ever'' folder. so you work on your character and keep posting (like the rules stated) status updates and hopefully get feedback from people so you know where to improve upon.
next step is checking your whole mesh for correct shading, because this is also influenced by UV shells, if you want to know more about that, read this: http://polycount.com/discussion/107196/youre-making-me-hard-making-sense-of-hard-edges-uvs-normal-maps-and-vertex-counts
so now after the shading check, you start your unwrapping. It is handy to keep in mind how you want to unwrap and texture your models when you make it/them, or to keep out the repetition in making models all day , you can unwrap some parts already to test out how certain materials/texures will look on them. I do not know what kind of workflow you will use so I can not tell you how to normal map and all that but do check out quixel's NDO. it is a Photoshop plugin for editing normal maps. I do not know how good the substane painter normal map editing is these days since I just use NDO most of the time but it might be wise to look into that. but after normal mapping in extra details it is time to texture it! make it any color you want but do make it fit in with the character you are making , this way you will have a much nicer character to look at. like a ''gunmetal'' rifle will look just like that, a rifle made of gunmetal ( the black metal) but if you have a rifle and put a pink panther texture on it, it will look like a call of dute camo and just silly. it breaks the immerssion of your character and the impression it will make is just gone. no mr bad ass anymore or a valkery of the battlefield. (imagine that though, a valkery of the battlefield in a pink tutu, wtf am I thinking) .
hope this helps. and god this took me 25 minutes to type atleast!
