So, I found out that Nike used little stickers to fill the numbers on the sole of my Vapor Pro Combos. Not sure if it's actually a sticker, or if the paint just turned out to be able to come off as a solid piece. Anyways, a couple of my irons no longer had black filling in the number on the sole. I'm the type of personality where this bothers me, so I set out to do some reading to find out the easiest/cheapest way to make them black again.
I stumbled upon a video that Anthony Taranto did where he showed a little behind the scenes look of how he makes the custom wedges. The guy leading the video asked him about an easy way for people who want to learn how to customize their wedges, and he said Sharpie Oil Based pens were the easiest way to paint fill. I picked up a black ultra fine tip from a local office supply store for $2.50 and set out to make my irons look complete again.
Wow, this stuff is easy to use! I used it along with a little nail polish remover from my girlfriend (it has acetone in it) and they came out great.
One of those is original and one of them was done by me. I don't think anyone will know the difference from far away, super happy!