Hi, I have been painting fan cels for a while 
now, and have fine-tuned my materials and 
meathods every time. Here is what I have found 
helpful - and recommend:

If you can't get proffesional cel paint (which i 
can't..) then use what I use: Golden brand fluid 
acrylics. THE BRAND MATTERS. Cheap stuff will not 
fly. Golden is one of the best brands of acrylic. 

And I use an acrylic medium called "tar gel". It 
helps extend the fluid acrylic - while also 
allowing it to dry flat (not bumpy), and look 
more "normal".

I paint on PREMIUM quality PREPARED acetate. 
Regular acetate or OP sheets won't give you the 
same results. Once again - quality matters.

The pen i use for the blackest and most permenant 
lines is by Staetler... i believe it is 
called "lumograph" or "something-graph" (i 
forget, and it's not here... ;;;)

I use very very small paint brushes. Size 0, 1 
and 2 are what i prefer - and I like to use 
a "liner" brush also.

Feel free to email me if you need more info

~Tara