LONG LIVE RUST, and in this case GRUNGE too! Love it. I am delighted to see the first few rounds of these kits built up rusty and gunky. Fabulous!
EYEGORE is very happy.
If it's enamel, quite a while, but most of the time, it's just a few days 2-5. Sometimes I fish it out and scrub it with a toothbrush, then dunk it back in for a couple of more days until all paint and primer are gone.