Layer, Transparency, Color to Alpha...
Holy **** it took me forever to figure that out.
But in the mean time I stumbled across scaling images, adding layers, merging layers, flattening and removing transparency, and inverting colors.
I drew my logo/signature with a pencil on a piece of paper and took the picture with my digital camera. I know it would look better if I would have taken more careful cropping but I just wanted figure out how to make it work first.
I'll have to make a brush later, it looks like that would make things a lot easier.