I 4th Blender. At first I was using it because it's free. Now I'm using it because it's awesome! The interface is scary but easy once you get familiar :)
Does your tablet support the Wacom wintab drivers? Your Photoshop version may only support that while not interfacing well with the drivers from your brand.
deep paint and photoshop :) ps tho the bitter ol interface does get on my nerves sometimes, would be nice with to get an update with a freshed up version.
It's not much, but here's something I made a while back. Nearly 85% of the interface in bodypaint I never touch. http://kman.cottages.polycount.com/images/temp/bodypaint_01.jpg
I think it will help a lot for making things be exactly as big as they should be. The biggest thing that needs to be figured out right now is the user interface.