A wire wheel on a grinder knocks a lot out pretty fast. A flap disc for cleanup. As I sit and think about it, that's the only way I've tried that works really well. I want to try the sand blasting with a pressure washer, but I don't think my pressure washer was up to the task. I forget why, but I left that thought alone. I think it was not enough GPM. Then there's the needle scaler.
After rust cleanup, maybe get the steel clean and dry, prime and paint. I don't do anything that important, so priming is never on my list. Just throw some paint on it, and on to the next. Clean and touch up later on.