Recently, I wanted to fix some of my paint-chipped Mizuno MP-14 irons. But I wanted to do it the correct way. So I emailed Mizuno and asked them for advice in this matter. They promptly replied that I should try something called, "Laquer-Stik Fill-In Paint" by LA-CO Industries, Inc.
After some creative Googling on the Internet, I found that Laquer-Stiks are sold by The GolfWorks. They seem reasonably priced at just under 3 bucks apiece and come in colors commonly found on golf clubs.
According to GolfWorks.com, "Using any sharpened instrument like a dental pick or nail, carefully etch the engravings or stampings, removing most of the original paint. Next, rub the appropriate color of Lacquer-Stik (See Pg. 6-4 of our Full Line Catalog for the complete listing of colors) into the letter or number cavity. Wipe away the excess color and the results will amaze you -- it looks great!"
The nice folks at Rite-Mark Stamp Company offered to send me some Lacquer-Stik samples to try. I received a black Lacquer-Stik to try on my Mizuno MP-14 irons. Below is a before and after pic of the sole of my 6-iron that was completely devoid of paint.
While the product was very easy to apply, it doesn't cure to a rock-hard finish like paint. Instead, it stays somewhat flexible and malleable. While this is great for certain applications, it's not ideal for something that strikes the ground repeatedly at around 80 mph.
I've been playing with the Lacquer-Stik filled clubs and they seem to be holding up. However, I doubt that they will last very long. If they don't, I'll try another recommendation that was given to me by a clubfitter: Testors model paint applied with a toothpick. Right now, that sounds like the best solution. I've also heard that nail polish works well, but won't be seeing me buying anything at any MAC store.
P.S. I'll try to keep the "Golf Deals" section in the sidebar current. Be sure to check out the free Pinnacle golf balls offer. You can't beat free! Let me know if the offer has expired so that I can remove the link. I think it will go pretty quick.