I ended up caught in a thunderstorm the other week while hunting with a 100 year old Mauser. It's not the first time I've dealt with it either. I have been caught skeet shooting more than once by rain and I remember a time a buddy and I had a shootout with our Ruger rim fire pistols and we kept going for a good 1/2 hour into some pretty gross rain.
When I got home, I used a hair dryer and a can of compressed air to dry it out. Then I sprayed WD-40 into every nook and cranny, then wiped it all down and sprayed it with canned air again. After checking it was dry everywhere I could get a cotton patch I gave it a light oiling and the gun was as clean as it has ever been. I did the same thing in the past with my shotguns and pistol.
I actually recently tore the Ruger completely apart and the inside looks great; no rust.
It's a bit redundant to use three different methods, but it ensures a thorough cleaning/dry out.
