Using RUSTALL with Miniatures
As the name might suggest the system is meant to create rust... on almost anything. It's a four step process. The first step is an alcohol-based rust-colored wash. The second is a water-based black wash. the third step is a flat coat and the last step is... dirt.
My first experiments have been interesting. The process was really designed for plastic model kits and model railroad enthusiasts back before the wide adoption of acrylic paints so the first step can be problematic. Since the rust step is alcohol based it's likely to re-wet the paint that you put the rust wash on if you do it too liberally. I would say that if you're planning to do the rust affect on a large area it would be important to make sure that you have a black primer coat underneath. The wash won't affect the primer and black works well under the rust color.
Your other option is to make sure that your paint has an enamel clear coat before starting the rust process. One of my experiments had a nice coating of Testor's Dullcote and that seemed to protect the paint underneath. This can create its own problem though because, again, if you use the rust wash too liberally and the alcohol sits on the clear coat for too long it can fog it - turning it a cloudy white. Fortunately, if you're going for a super-rusty effect this doesn't look bad at all. I noticed this happening on wide flat areas where the rust wash would pool.
So, armed with this knowledge you're ready to try this out on your own minis. Well, here's some other stuff that I learned. The process is a time-consuming one. Since you can't put the rust on thickly you have to build it up. This means doing a coat, letting it drt, then doing another coat. Repeating as many times as necessary to get the rust to the level you're looking for. Once that's done it's time for the black wash. It's a thin wash so, again, you have to do several coats to get it where you want it. Once that's done you do the clear coat. I've only played with this a bit but it really does seem to do a good job of making the finish dead flat.
The last step, the dirt, is really optional. It does a good job of making something look like it's been sitting outside collecting dust and dirt. It's not something you want to use on everything. Also, it's unlikely that you want to use it on gaming miniatures as there's no real fixative for the dirt which means that it will get wiped off with handling.
So far I'm pretty happy with the results, but the extra time required to get a good result means that this isn't something that you want to do on your line troops. You're going to want to save this for adding that little bit of extra effort to a mini that you're going to put in a contest or something similar.
You should be able to find RUSTALL at your local modul/hobby store or you can just buy it from RUSTALL.com.