Anybody know any good step-by-step instructions for going from a 2 1/4
inch plug in a vertical 'plastic' drain pipe (at the floor level)
inside the wall to the washer's outlet?

I know, I know, a search but you guys KNOW this stuff and can do a
simple paragraph *and* most importantly any 'gotchas' .

Embarrassingly, over the years I have NEVER gotten a drain system to
work right, always leaked/dripped, ie around one of those work sink
drop inlets, no amount of plumber's putty, nor teflon tape ever solved
these types of problems. Even a simple J-Trap would start leaking in
less than a year! In defense, it was one of those 'thin' metal ones
from HD and our chemicals ate through its lowest section. THAT taught
me to use plastic, but still...I finally gave up and simply put
plastic glue on the threads. Now THAT worked. but posed other
problems.

I would like to avoid that permanent scenario this time. Future
cutting the pipe out of the wall is not a viable option.