I see 25 lb. bags of "patching plaster" for sale and 25 lb. bags of
"Fix-It-All" for about $2 more. Which is the better buy?

My 90+ year old house is mostly lath and plaster and there's a lot of
bulging and fallen away plaster.

I bought a trowel and made a hawk and am ambitious to learn and apply
knowledge on plaster repair. One guy told me he thought it would be
better for me to put up 1/4 inch sheetrock on a ceiling that has a lot
of falling plaster. My sheetrock experience is nil, but I have some
pieces from a leftover sheetrock job.

Hopefully, a foundation removal and new foundation and house leveling is
in the works here, and I figure I should hold off on complete plaster
repairs until after that, but right now, there are some areas that I
think I should/could maybe tackle sooner.

TIA for guidance.

Dan