Nopoop,
To create the shading try playing with this....
1. First, mask out an elongated rectangle along the edge you want to make a shadow over, make sure it's at the right angle you want. the witdh of the mask will determine how far out the feathering (gradiant) will go.
2. In the palette option, the forground will be black, and the background should be set to no color.
3. Goto the brush setup and use one with a larger size then the mask.
4. Goto the forground color setup and instead of using a solid color, set it to gradiant.
Now here's where it might be different for you, depending on what program used for painting. I use PSP 8.1 and they have a number of gradiant option. I can set the style of gradiant, forground to background feathering, or visa versa, and I can set the angle of the gradiant too.
5. I'll set the angle of the gradiant to the proper angle of the surface i'm working with, and make sure the masked portion is where I want the gradiant shadow.
6. I have the gradiant set to forground to background color.
7. Using the brush I setup earlier, I'll make a pass over the masked area and try to do it in one pass. successive passes just doesn't look right to me, so it usually takes me a couple tries.
Hope this helps bro