Hey all, thought I would throw this out there. Took pics when I did this today and I am really happy with how it turned out.
(Screen Accuracy Fanboy Warning: my work is close, but not dead on to screen acc. I used the MOM pics as a subtle reference. Personally I am going for the realism look and don't care about the hardcore details. So if you want screen acc., don't go by me.)
Tools Needed: Rotary tool (dremel), diamond bit engraving attachment, pencil
1: Use your reference pics, or just go off the cuff and with your pencil draw in the areas you want to look distressed and scratched. Think ahead to your painting, and remember these areas will be showing more silver to give the appearance the helm was nicked down to the metal.
2: If your rotary tool has a speed setting, keep it on a low and controlable speed. You don't want to lose control of the tool and make an unwanted nick or scratch in your helm. Trust me, these things get a mind of their own sometimes. Don't fret though, just keep a steady hand and have patience.
3: Now, start "drawing" slowly over your pencil drawn scratches with the rotary tool. The engraving tip is almost like using a pencil, just a little awkward to hold so again go slow and keep it steady!
For scratches, move back and forth over the drawn line in even strokes putting a very small amount of even pressure. You don't want to go in extremely deep, but you will see it slowly start to engrave the surface away and create your cut. For realism, make the scratch deeper in the center. Or you could make it deeper at one end, and less at the other which gives a cool "ricochet" look in the helm.
For nicks, simply grind out an area wider than a scratch using the same process. Safe and slow! Nicks are more for around the visor area. Remember to get the visor's indented inner lip along with the front surface. You can see a good example of this in my pics.
4: Thats about it. Now when you do your painting, those scratched up areas will look a lot more realistic upon closer inspection.
Thanks for reading.