FYI, never use isopropyl to clean automotive stuff. Isopropyl is "rubbing alcohol;" it is used for medical purposes and thus contains a small amount of oil.
Denatured alcohol is pure and won't leave an oily residue.
On fittings I use a wire wheel on a bench grinder. The stuff gets pretty stiff after it's been on the car for while. A wire brush and spray brake cleaner would be the second best option.