I use one for warming decal water and I have found that it works great for me. You need to be careful not to leave the decal in for too long as it will float right off the backing paper. Especially the little ones.
I don't think Don was talking about warming paint cans (although that would work too, with the water not directly), but as a paint dryer - the heat from the warmer causing the painted part to dry faster. I would be hesitant, not sure how hot it would get and the part might not react well to that.
Paul