On the siderails, I had success with an automotive pick hammer and dolly - you can get them flatter than with just hammering the low spots alone. Then, you have to do a decent amount of polishing just to see what the repaired areas really look like. if you get the dents popped out a little high, you can file them back flat faster than you can sand/polish them.
In my experience with beating out dents, the block sanding instead of going straight to the wheel really helps hide a lot of sins. A real metal finisher can make them look like new but it will take them more than two hours, therefore not cost effective v/s new rails.