Well, in order to make actual anti-tank round hits you might want to drill a small hole, and DONT PUNCTURE the plastic. Then, with some tamiya puttty and a sharp toothpick, make some "melted metal" around the hole, kinda build it up so you've got some thing that looks like battle damage. If you got to missing-lynx or ww2modelmaker and look at the Tigers, you can get a good idea. Then you want to paint them dark, dark grey, almost black, then dry brush very lightly with a metalic color and then take some rust like pastel color and add some rust, not a whole lot. Also when making the metal build up, make 2 or 3 streaks coming from the hole to make it look like the molten metal splattered.
hope this helps