Hi there, 
Ive TONS of cels, so I can tell you exactly what 
you need to do, in fact, today at lunch Im goint 
to the blueprint place to pick up my line art for 
my new one!

First of all, if you want your line art to look 
really clean on the cel, you do NOT want to trace 
the lines yourself onto the accetate.  While some 
people think it's more "artsy", it is VERY hard 
to do if you dont have the right tools, which, no 
one does, unless you work for an animation 
house.  What I do, is make the line art on paper, 
or a graphics program, and then take the line art 
to a print house, or copy house, like Kinky's 
(Kinko's) and have it Xeroxed onto the accetate.  
Depending on the size of your cel, the largest 
you can get this done at is 11 x 17.  Mine is 11 
x 16, and I had a really hard time finding a 
place to do it for me.  But, if it's just plain 8 
x 10, then anyone can do it!  As for the kind of 
accetate, there is really only one kind.  Just 
make sure you get it thick enough.  0.5 thickness 
is the normal.  Also, if you do take it to a copy 
place, they have their own accetate they use that 
a copier machine can pick up correctly.

Paints, you can go to any hobby shop, Hobby Lobby 
is best,and go to their bottled paints section.  
It is usually with the wood crafts and ceramic 
crafts.  The paints are Ceramcoat, Folk Art, and 
Apple Barrel Color's Plaid paints.  Any of the 
bottled acrylic paints are great, but Ceramcoat 
has been my fav so far.  Plus, there is EVERY 
color you need!  The only thing is, they take 
forever to dry.  You need to litterally glop the 
paint on, very thick if you want to avoid any 
thin spots where light goes through.  Like, put a 
glop of paint on the face, the with a small 
brush, move the paint around.  You need it to be 
thick, but that means a long drying time before 
you can continue with another layer, for like, 
higlights and things.

The paint will not crack, not if you use the 
bottled acrylics. The great thing about these 
paints, is that they are pretty much liquid 
plastic.  When they dry, they form a sort of 
rubbery patty.  You can look at any real 
animation cel, turn them over,and feel the back. 
The paint is very flexible.  I have two anime 
cels that I made a few years back, and they are 
still perfect. I dont know about 5 or 10 years 
time, but they should hold fine--and I laid some 
really thick layers onto them.

I dont know how to get a transparent look, you 
may have to ask about watercolors at the store. I 
dont know if there really is a way to do that, 
you have to fake it I think. But, that's 
something I have never tried.  You start with the 
extremes first, like shadows and highlights, then 
go to the medium tones.  Just be careful about 
the layers, dont accidentally paint a shadow, 
then notice that you had a highlight that was 
supposed to go on top of the shadow. 

I hope I was able to help, if you need any thing, 
write me personally.  Ive done this about 54 
times :), so I know what to do on most things!  
Good luck!  Here is my fancel that I am about to 
start painting, I know I have posted it before, 
but I really am proud of it!  Enjoy!