ive used poly-urethene , in various forms on lots of old " bubba " modified guns.........( canadian tire brand , helmsman spar varnish my favorite, varathane, ect, )
the matt finish ones end up looks best otherwise the gun looks tooooo shiny /plastic like. ( in my opinion. )
usually do 2 coats, let em dry through an through, , then litely rub with ooo steelwool, with off, an 2 more coats , then good to go after drying.
NOT FER COLLECTOR GUNS OR ANYTHING REALLY VALUABLE........BUT if the gun is a yard sale special, they usually look 90% better after a good clean up an a bit of re-finishing. also a good way to pass a week-end during a sno-storm .
nuff said , if this is a SIN sry in advance.........