[Dang, Blogger is really having fits today. I posted this earlier, but it's just gone, it wasn't even there as a Draft, so this is a quick re-write.]
Adobe Eazel seems promising. It might have a bit of a learning curve, but the videos, the lower one especially, shows that it can do some rather amazing effects I have not seen before, certainly not on a tablet. I have paid for the top-dog app Painter at least twice in the past, but I was never very impressed with it.