Went shooting on my buddy's property this past weekend, was very heavy fog so my 30-06 was soaked. I dried it very well before I left inside and out. But apparently there was enough moisture inside my case, because I open the case today to find rust all over my rifle. I used some wd-40 to clean that up pretty well, but I can see some spots of rust in my barrel. What's the best way to clean it up?