Working with Copic/Prismacolor marker help.

I have a final project in which we need to render textures in a surrealist environment using prismacolor markers.
I have warm grey 10,30,50,70, and 90%.

The problem is, I really really REALLY suck at any type of foreshortening, and imagining how to place a light source on a texture object is the death of me ;-;

To give an idea, say I wanted to mimic this texture, but apply it to a sphere or cube instead of a flat surface:


How2render?

Does anyone have any tutorials/advice that could help me? I've tried and it just...sucks.

Best I can offer up from google :\ http://www.ehow.com/how_8662543_render-u...arker.html

I would say layer it out with the shades that you need where they should go, and then blend them appropriately. Soft blending for where the grays really meld together, and hard blending for hard edges.

Do note though, I have zero experience with markers as well.