Mine is similar to Harry’s. Also stainless steel.
On tight ones or on ones that are chewed up
I clamp my tool into a vice. Then I can push
the mixer into the tool hoping the tool will
stay in the slot till I can get the cap to break
loose.
If they are so bad that wont work I clamp the
cap in the side of the vice and twist the mixer
to break them free. The jaws of the vice must
be straight and square for this to work or the
cap will slip out. Brass or aluminum jaws
prefer but if there really chewed up it really
doesn’t make that much difference.
Tubs.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.