Yes plumbing caps.. black rubber with an aircraft clamp around the edge... if it;s too flimsy, just cut her down a bit shorter to stiffen the rim.
Also if yoyu grab the cone of the lens.. it will unscrew ofmr the lower portion of the lens barrel. It will come up maybe high enough you can grab the rim of the ring with your finger n twist her out easier that way. It;s a common sence thing. you'll see as you get it started.
BTW this is the hard part.
Oh once we get to taking screws out.. put em in a pill organizer so to keep em with the step we are at. It makes a differrence in types of heads n threads when reassembeling step by step.
My work surface has a thin excersize mat so it won't marr the lens, screws n things can't bounce off or roll either.
Good light n stay neat.
Have fun n enjoy the ride. You may adopt a new hobby.. restoring cameras.