I made a stencil out of a thickish plastic folder with our sons name on it, I used it on his stuff. It is about 6 inches long and about 3 inches wide. I use a household sponge dipped in paint to fill it in, not to thin, or too thick.
I also use his letter stamps - with fabric paint mix added to his normal paints, or I use fabric crayons, and a fancy font from the computer.