Heres a little tip about the cardboard. I've been using it for about 2 years now, nothing else, and ive got the perfect system to make it look as real as possible. Before painting, take masking take, and put it on top of the visible corrogation. Next, use glue, and with you're fingers aply it on the edges of the tape once its on the cardboard. Make sure the glue covers the tape, so the edge of the tape doesn't come off, and so the glue creates a "ramp". After you're finished, paint the gun, and you'll find that its almost impossible to see the tape. You can't see it from 15cm away If you do it right!
CHEERS!