I would recomend going to home depot and buying a $2.50 pot of BEHR Paint and primer, the flat exterior kind. Stuff goes on thick in one coat and is fairly hard to scratch, I'm not sure about its wear qualities on something like a hand guard(where your sweat and grip can wear it off), but it looks good for using on optics. Also dries in like 20 minutes to final hardness.
Feel free to message me if you need assistance with a WE-scar, gbb maintenance, or any maintenance for that mater, I'm around and checking.
WE SCAR, "King's special" (in for repairs)
Cyma AK-47 - "bloodbath"
KWA Mac-11, for making things loud in a hurry
Tanaka m700 breakdown, for those rare situations when I don't actually want to be seen