I’ve seen people use crayon for stuff like that before. It comes right out, so you could do that to see if you even like it before you start throwing paint around
It’s generally seen as the hallmark of an amateur…but if you’re dead set on it, AR15.com will have plenty of resources for you to conduct a search/ask for advice.
I have used Tamiya model paint on golf clubs before as the factory paint wore away and it has held up awesome, even with the abuse they get from constantly beating the ground.
These “color in my roll marks” threads always seem to end in drama, so I’m going to shut this down before it goes that way since the question seems to be answered.
If you really want it opened back up, feel free to PM me or another mod.