You could use a heated needle or nail sized according to calibre impact.  As your doing it be vigil to the angle, depth and amount of metal displaced by the ricocheting projectile and use a sharp x-acto blade to finesse it. I came across this modeled KV with heavy projectile damage for reference.  Good luck.

if you mean holes as in penetration, it just didn't happen. there are numerous pics of the KV-2 that held up IIRC the 6th PZ DIV for 2 days. nothing penetrated the hull and turret. i'm not even sure how big the gouges would be from a 37mm. i would look for pics of battledamaged TIGERs and JAGDPANTHERs to see what a non-penetrating 75mm or 76mm looked like.

I think that bullets would have very little effect on a KV-2,probably would look like small chips in the armor,unless you make some holes in the front fender or tool boxes.

Recently, The Doog posted a pic of a projected where he used an awl to simulate bullet holes. The only thing is that was on a photo-etched side skirt, I think.

But you might try it on a scrap piece of plastic first.

Hope this helps..........

Scott