Most Poly doesn't have to just dry, it needs 3 days to "cure" fully. Paint pens and Sharpies use solvents that will melt through uncured poly.
Your best bet is Industrial Sharpie's if you go that route. They are clearly marked "Industrial" in red.
I use india ink. It's really cheap and can be found just about anywhere, art stores, walmart, craft stores, etc. You can sharpen a stick to a point and make your own "pen". Fine caligraphy pens (again, super cheap and found right next to your india ink at the store) are pretty good to use too. India ink is water based so it will not screw up your finish even when you are too impatient to let it cure.
A light spray-coat of poly over any lettering and then a few successive, heavier coats will keep it there for life as long as you don't scratch it off. India ink will not fade. Consumer Sharpies will. Industrial sharpies will to a lesser extent.