Someone posted a message a couple of weeks ago asking about doing winter camo on armor. I scanned through a few pages and didn't see it. Seems like it had a few links in it, but I ran across this one on Tamiya's web site and thought I'd pass it along for whoever asked the question.
http://www.tamiyausa.com/articles/feature.php?article-id=36
There are several good articles on the parent page for that one:
http://www.tamiyausa.com/articles/index.php?id=1