I was cleaning my granddad's old side by side last week and the firing pin spring was totally seized up. Nothing I tried at first would get it to budge, not even penetrating oil. I ended up soaking the whole assembly in a mix of acetone and transmission fluid overnight, which I read about online. The next day, I used a small punch and light taps to work the spring loose bit by bit. It came free without any damage, which was a huge relief. Cleaning off the gunk showed it was just years of built up grime and a little surface rust. This method saved me from having to order a new part or force something and break it. Now I tell folks to try a long soak with that mix for really stuck small parts before going harder on them.
Hand reaming gives me better feel for the metal than power tools ever did.
Stretching breaks keep my hands ready for detail work.