It's a fairly simple procedure, that you will no doubt already be aware of.
1. Place your craft knife on the area to be Bullet'd and then twist it untill you develop a hole as deep as you wish.
2. Using your knife, place it in the hole and press down on the edges untill your knife sinks in somewhat.
3. Rock your knife from side-to-side a few times to widen the tears, and to raise them slightly (Like a welt).
And you are done!
Please note, this only really works for Non-explosive rounds, such as Slugs from a shoota boy, I'll do another tut for Bolter rounds (Which apparantly Explode under Skin-Armour.
Unfortunately, My camera does not like to take photographs of small objects such as this, and this means there will be no photograps of items as small as this.