it depends on how much this rust as got hold,its commonly overlooked but the rust could be along the whole bolt in the wall too,all can be done is the good stiff wire brush and a rust cure on the visable parts and grease after.
i took the whole thing down earlier this year and sprayed the dish hammerite the brackets and wax oild the rest,it works better then ever having moved the brackets,if removing a rawl bolt use a quality m8 thread and hammer it back in and the old m8 should come out and its possible to use the same holes if needed.