ear buds and acrylic paint for me. I bought a tube of black and white from ebay- probably kids paint I think, but it was cheap at a couple of quid.
Do you also paint the tubes Jim? I have tended to do one or the other, but get better results with doing the inside of the blank rather than just the tube.
I had wondered about nail varnishing the tube. I tried the marker pens and that worked ok. The downside of painting the blank is that it normally needs 2 coats, so i have to be even more organised to do a batch. cut blanks to size and drill, a coat of paint at night, a coat before going to work, then glue, wait and turn. This pricess can take me a couple of weeks or more due to available time in the workshop.