In terms of battle damage, you can us a pin vice and a small drill bit (1mm diameter or so) to make lines of bullet holes. If you want larger holes you can use a larger bit, or use a craft knife to scrape out the top to make more of a crater.
For near misses on corners and edges, you can use a knife to slice out a crease as if a bullet has slid along the surface.
For energy weapon hits you can get a good effect using a soldering iron, just be careful not to breathe in the smoke that comes off as
raw styrene monomers are not good for your lungs.
For exploding impacts you can superglue on little bits of clump foliage and apply a bit of
OSL.