Stripping paint. I've built up a pretty respectable shop from used machinery ( 35 stationary machines , the newest from 1961, the oldest from about 1890 or so), all of which was completely dismantled/repaired/restored. Some machines were in wonderful shape, and some were absolutely terrible but hands down, the most obnoxious part for me is always the paint removal.
You might try using a needle scaler. Harbor Freight makes a pretty good one cheap. It does an amazing job particularly in those hard to get at concave areas. Much easier than sanding or wire brushing. Very little damage to metal surfaces.
Randy