On my woods I crest with Sharpie pens, then spray a very light coat of clear lacquer or acrylic over the cresting. It protects the cresting from rubbing off, but you have to be careful with fletching glue compatibility with the spray. I crest an area under the fletching too, and last time I used the wrong spray for my gasket lacquer and had to reglue a bunch of them when they popped off. I used superglue, should have used duco. The superglue worked fine the time before, with a different kind of spray. From now on I'll stick with the duco, or just not spray the fletching area.