i have only done a few. I used a cotton bud, and it worked ok. I think that the non polished surface of the drilled hole didnt help get a uniform covering, and I had to give it a couple of coats. I prefer to do this rather than to pain the tubes, because it saves having to balance tubes on end. Also, i perceived it to be less messy.
I knew that the paint colour would have an effect, but I had 2 of the same blanks. One I used white paint and the other black- I wouldn't have believed that they were the same blank if somebody had told me.
