Never steel wool on a firearm, unless its to prep the stock on a shooter or field gun with no collector value. I use acetone. If that doesn't work, step it up to Blix or one of the chemical strippers for antique furniture at Home Depot. Stretch a wire coat hanger (unpainted), one loop in your triggerguard slot, the other over a tree branch. Spray the stuff on there and let it do the work. Wipe off with a towel, or at most a nylon bristle tooth brush. Repeat. Be careful of any stock markings. Light wipe after that with HFW or even some boiled linseed oil.