[Snuff]

I use mostly C-tex and It can be a real pain. The best stuff Iv'e found is Liquidtex Flow Aid. It mixes with water and is pleasant to use. For really crappy paint I foundthat about 5 drops of dish soap in 16oz. of water will thin the most stubborn paint.
It works by making the water "wetter", and by reducing the surface tension of the water. I havn't tried it on T's yet (you gotta get a good bond) but for bike tanks and helmets it is da bomb. It also gets rid of the graininess that pure water causes.
You do have to reduce your air pressure to avoid spiders.