I personally really like RCS liquid mask from Jon Miller (rcsgraphicworx) it goes on nicely and peels off a treat.
There are others such as Fasmask which is ok and Bob Dively (incredibly hard to get hold of over here but also heard really good things about)
If I were you I'd get the rcs stuff, either from xfactory (distributor), or order through your local hobby shop or through the rcs website.
