For many years I used nail polish on my guns. These weren't recessed dots, usually a channel and blade.
The nail polish started to wear off very quickly with carry or cleaning.
Sure it was cheap, as I was using stuff that my Wife bought and later decided "I don't like that color any more", but Bright Sights is well worth the difference and one bottle will do a lot of guns. I have yet to have a need to do a re-application on any gun.
I do have a lot of guns that need to be done, but all for the first time.