Welcome to Librarium Online!
Just started a small group of orcs as a side project and need help with weathing and battle damage effects. If anyone has good tips or a good link then please share.
One thing i noticed that works well with just about any Ork metal, thats quick and easy - Take a big fluffy brush, put a dab of boltgun on it, wipe off just about all of it, and then sweep along the model just as you would with any drybrush. Do this and then Tin Bitz following the same method and it makes any tank look Orky. Do this after you give the tank your desired color scheme, and the paint will look dusty and worn. Go even further and give the model a wash with Gryphone Sepia by brushing downwards - and it gives all the rivets that rusty look.
You can represent battle damage by painting a black gash starting on the edges and moving against the direction of travel.. Take Boltgun metal and fill that black in leaving black around the edges minus the initial corner.
This works even better if you are willing to use your hobby knife and actually carve those gouges and gashes yourself... Appears to be a deeper scrape that way.
Also drilling holes and creating star patterns around it give the effect of bullet holes. Remember when you do this that the angle the bullet hits will change the star pattern... For instance, a left to right impact will result in a single longer star tip on the left with a couple small star tips on the left on each side of the long star tip. This will then result in broader star tips on the right side.
When it comes to painting the impact holes, same method applies, but then you need to decide what made the impact.. Lazers will scorch along the impact.