You might try phosphoric acid to attach the rust. If you apply it in a way that it stays wet, i.e. a wet paper towel covered with plastic wrap you can let it sit and it will take less work. I alternate between acid application and wire brushing. I can get a clean but pitted surface without making the metal as thin as you would with a grinder.
Be careful if you are working close to seams not to get the acid in there.