Just be aware that most all common toothbrushes will start to disolve/melt when acetone contacts them.
Get as much of the 'gold' out of the markings by wiping it out then go at it with the toothbrush and minimum acetone. Lacquer thinner will do the same to most toothbrushes and soften and melt them.
If you're not carefull you can have an awfull mess on your hands and gun with disolved plastic as well as the gold.
If you happen to have on of the M16 cleaning brushes (toothbrush type) handy those work the same and I haven't found any solvent yet that attacks the plastic handle or bristles of them.
Keep any solvent, especially acetone or lacquer thinner away from wood grips as it will remove any finish on them.
Pachmyers too. Scrubbing away at the markings can splatter the stuff around pretty well. Any splatters landing on the rubber grips and then quickly drying, will leave the gold inlay matr'l they may carry behind on the grips. Just extra clean-up.
I think nail polish remover is mostly acetone, but there are some non-acetone removers too. Either would probably work.