A few people have asked Stencil Archive for tips and info on spray painting stencils on t-shirts.
Some tips I've given them are mostly screen printing tips:
- use a flat palate (piece of wood, glass, or even marble) to keep the shirt flat
- make a mark in the middle of the palate so you can center your shirt
- maybe use spray tack to keep the shirt from moving
- put the shirts out in the sun or in the dryer to cure the paint
- if you want tight lines, practice improves your skills