The problem with brake cleaner is it works to well. It’s a must to go back after using it and lubricate everything properly. A mechanic I know used brake cleaner the had parts lock up from gallingTry brake clean, it dries up fast without leaving a residue and it's not flammable, get it from the auto parts store. Don't get it in your eyes. I'd spray it with brake clean and use an old tooth brush to work it off. Then leave it soaking in Hoppes No.9, keep scrubbing with the tooth brush. Make sure the gas tube and piston are free of the crap too. I had a friend that was shooting one that was still filled with cosmoline, the thing actually cycled but was slow, lol. I'll bet the tool kit and everything is caked in that crap.