If you use cheap paint or markers, not only does it wear off fast, but makes the ball dirty, real fast.
I remember in high school days, I used nail polish, since it was like enamel but it stuck the crosses together and made the racket feel a little dead. Also, it didn't stay on too long.
Now that I'm older, I like it without and stencils. Afterall, why advertise if I'm not getting paid for it. Back in the 80's, I really liked having a ST logo on all my tennis clothes. Now, just plain stuff is good enough.