Get some safety gear like a face mask or respirator, eye protection and rubber gloves. You need to be aware that spray paint is very toxic and you don’t want to breathe it in especially over long periods of time. If you are spray painting inside, get a good respirator. Remember it’s always good to be safe than sorry!
Well, on to the garment stenciling!
Garment stenciling with spray paints on fabric is a little more of a challenge because fabric can move and stretch. I coated the back of the stencil with a glue stick. It kept the fabric from stretching and secured all of the stencil edges against the surface to reduce over-spray.
Unless you are using a paint that is specifically made for fabric, the finished image may be stiff and there is no guarantee as to how it will react in washing. Read all directions on the paint you are using and experiment.
I put a piece of cardboard inside the T-Shirt for a couple of reasons. First, is that it will keep the T-Shirt from sliding around or getting wrinkles. Second, it will help prevent paint from seeping through the fabric and leaving an image on the back of the T-Shirt. You want the cardboard to fit inside the T-Shirt without stretching it in any way.