I did the bearings about 5 years ago on a boat trailer -- so I'll share my experience. If it was a perfect world everything would have been quite straight-forward. Somewhere along the way, one of the inner bearings ceased and was spinning on the axel - this caused it to wear a 3/8 grove into the axel. I spent about 5 hours on that wheel alone. Ultimately blow-torched the bearing chase off the axel, then ground the lip that had formed from wear. Kind of scary when I think about what could have happened.
I was going to do brakes on that trailer, but the bearing buddies had pressured a lot of grease around the bearing seals, so the drum assembly was totally caked with old grease. I decided to forego fixing the brakes. If I recall correctly, on my trailer, the drums were the same machined cast metal as the hub. It's been a while, but I think replacing the drums meant replacing the hub.
I don't mean to tell you something you may already know, but one of these is a safety thing and the other will make your life easier.
first, As far as tightening wheel bearings, the trick is to tighten as tight as you can with your fingers, then back the castle nut off until about an 1/8 of a turn until you can get the cotter pin through. Then check them after the grease has had a chance to wear out of the bearing.
second, buy a bearing packer and grease gun. Saves a lot of time over packing them by hand.