To make real rust on your armor, you'll need ferrous powder. I buy mine from a place called "The Compleat Sculptor" (yes, incorrect spelling is intentional!) Here's their list of fillers; the metal I use is the "Iron Powder - grey (325 Mesh)" (pic 2)



I have tried a couple different methods, but my current favorite is to take two paintbrushes, the powder, and a cup of water to apply it. First brush is saturated with regular water, then brushed over the area on your armor you want the rust to stick to. Take the second brush and scoop a small amount of powder onto it, then tap it lightly over the wet area to apply the powder. Wherever the piece isn't damp, the powder will fall away (pics 3-6).



Next up, get a disposable spray bottle (old Windex bottles work great here) and fill it with a mixture of hydrogen peroxide, vinegar, and salt. I mix these together in a 6:4:1 ratio by volume. Shake up the mixture in your spray bottle and set the nozzle to the widest mist setting, then spray lightly over the metal powder (pic 7).



Just to give you an idea of what to expect when you're spraying, initially the rust powder will make a sort of nasty yellow foam. This can be immediate, like right before your eyes, but sometimes it can take a few minutes as well. You can see this happening at about 2:58 in this video below (it goes by quick!)







This will fizzle down and settle into a nice rust texture pretty quickly (about an hour or so) but don't try to blast away this bubbling with your spray bottle! That's the chemical reaction taking place, and more accelerant will only remove the metal powder.



This kind of technique is a bit messy, and it can get away from you in a hurry if you add too much powder or accidentally blast all of the rust to an area on your piece where you don't want it. My advice is to start small, you can always add more after you've finished a coat, and a little powder will go a long way. You have spray carefully and make sure you get a spray bottle that doesn't jet out or you'll just blast away all the metal powder.



Things will look like pic 8 after spraying. You'll have some runoff which will be tinted with the color of the rust, but if that's a problem you can always buff it off with a scotchbrite pad later. Make sure to put some scrap cardboard under your parts to avoid destroying your work surface. Oh, it will also smell like hamster pee.



I let the rust cure for 24 hours before I do anything else to it, and initially it will look pretty grisly. Once the peroxide and vinegar are gone, a lot of salt is left behind, and it's not very pretty (pic 9)



A quick buff with a green scotchbrite pad will get rid of this (pic 10, 11, 12)