>Actually, I've been looking at the paints that they use to 
>paint the Warhammer figurines because it's supposed to be
>formulated to work on plastic but I have yet to try it on
>cels...I think I'm actually gonna give it a go on glass to
>see how well it coats before I go that far.

The paint used to paint Warhammer figures are those teeny
bottles of enamel based paint. 1 dinky lil jar will cost
you anywhere from 3-5 dollars(unless you find em on sale
but stil...)
They will work quite well, but as you can see, they're damn
expensive!

I had some acrylic paints left over from my art class and I
wanted to do a custom cel for her birthday.
Acrylic based paint will adhere to plastic surfaces quite 
well. So, to answer the original question, the acrylic 
gouche *should* work.

The forumla that I used and works for me is medium viscosity
acrylic paint, *OR* high viscosity acrylics along with some
flo-ease.  Flo-ease is a product made by Golden Art Mediums
that will loosen acrylic paints like water without 
destroying the binder(the chemical that holds the paint
together.)

Good luck creating your cels!

~Pharna.