I don't mind if you ask for advice and then want to sell your creations you silly filly~ You can do whatever you please.
I use Super Sculpey for the hair, tails and accessories. Super Sculpey is a type of polymer clay and it's sold in 1lb blocks. Sculpey also sells smaller 4oz packets of clay. You can find them at most art stores. You don't necessarily have to buy Sculpey brand, there are several other brands that are useable as well. Just follow the directions on the packet and you'll be fine
As for painting, I use various brands of water-based acrylic paints. In order to get a smooth paint job, it's best to put a few drops of paint into a separate container and water down it down just a bit. You will have to paint more layers but the end result will look marvelousssss~
If you have anymore questions, you are welcomed to ask.