The Guzziology book says to just destroy the sludge trap plug when removing. They tend to be seized, besides being punched to further lock up the threads. My plug was punched in the 6 o'clock and 12 o'clock positions and was super seized. Allen key wouldn't free it, hammer impact driver wouldn't work, impact gun succeeded only in messing up the hex slot in the plug. My plug was stuck and I don't have a M22x1.25 tap to remove it, so I took it to the old timer machinist over the bridge to drill it out for me. $20 later I have a nice crank with very little stuck in the sludge trap.
I used a special factory tool to clean out the big pieces of sludge. Chemical cleaning with a brass brush will happen later.