A lot of people here have made those type of 
correction layers. I've made a couple but they're 
kind of a pest to make. The more lines there are 
(or the tinier the lines) the bigger difficulty 
you're going to have getting it to match up 
nicely to the cel.

Check the archives and you'll find some excellent 
suggestions for pens and the like. ^_^

Many Sharp Smiles,
--Drac