Anodizing and painting are both surface treatments which can ding off and reveal a bright aluminum surface.
The GSG body is anodized and the spoon and detonator head are painted.
The pin pull isn't too hard, but I wouldn't wire it for a tripwire application. As a booby trap, the best bet is to hold the spoon down with something (say push it into a cup) and use the tripwire to pull the device out of the cup. You would want to use some sort of ingenuity to let the wire pull free of the device instead of having it drag around everywhere when the wire is pulled. Tying off directly to the grenade would probably have the grenade getting hoofed into the bushes if a runner hits the wire fast.
Want nearly free GBB gas?