Spray with Aerokroil then get a blunt point in an air chisel to try and drive bolt out. The impact plus vibration might get the rust broken loose then try going forwards and backwards with the impact to try and finish breaking the bolt loose from the bushing and get it turning. The blunt point in an air chisel works wonders on stuck objects. Wear eye and ear protection for sure.

If your not trying to save the rubber bushing the other methods mentioned will work fine too.