Okay, so this is pretty easily explained But instead of typing I'll make a twitch video and post it tonight I'll take one of your faces here and do it. I'm not syndicated with twitch so it will only be up for two weeks so you'll have time to watch it at least.
It will take me longer to type out the explanation but maybe after I do it I'll be able to make a bullet point tutorial for you to use with lighting. Twitch link is in my BroBook artblog thing.
EDIT:
@Barry
Okay the video is up and it will be gone in two weeks, unless I upload it to youtube. Its late and I am not an actual teacher and I'm just trying to help out with some principles. Here's the final of the 30-45min. Demo.
Hope it helps. Take a grain of salt with this because remember you are the artist and this has my aesthetics in it now and not your artistic license. Hope it helps and makes sense.