Patching and Plastering - Advice Needed: Plastering and Plaster repair

My wife and I purchase a ca. 1925 house about a year ago. Due to settling and/or age, there are a lot of cracks in the plaster and some separation from the lath.

I have decided to do the repairs myself. After reading an article on here, I got some patching plaster, a chisel, a couple different sized applicators and went at removing the old plaster and redoing it. The article basically said - clean out the old plaster to the lath, wet the lath (or use bonding agent (which i could not find at Home Depot), put on a couple layers of plaster, finish with joint compound, sand as necessary, prime and paint.

Fine. Did that and it was more or less successful (those walls have held for several months now and appear/feel to be more solid than most of the other walls in the house).

Skip a couple other minor repairs (that one was about 4 - 8 sq ft.)

NOW i have taken on the hallway. It was all wallpaper, which is not all gone. Apparently, the wallpaper was the major structural force in the wall, because half of the plaster came off shortly after. Needless to say, there is alot more repair that is/was needed. I used my saw to cut out the affected areas (i found that this gave me cleaner edges than trying to chisel) and I am nearly to my final coat (although I have now switched from patching plaster to "Fix it All" (or something like that in a green bag), because i accidentially discovered that it was much easier to work with than the patching plaster.

MY NEED: what tool(s) are the best for leveling the new plaster with itself and the surrounding area dealing with large spaces. I have been trying to do this with a finish trowel and a few putty knives (2 - 12 inches), but i feel like a big board with some sandpaper would smooth out bumps in more efficiently (plus it is hard as hell with the trowel).

I can go buy the tools, but the people at home depot keep giving me various sized putty knives ... no offense to them, because without them i would still be using lightweight patching materials ...

Any advice would be appreciated. Also, if any plasterers in SF Bay Area would like a free helper for a few days just so i can see professional plasterers at work, let me know.

I'm not sure but it sounds like you have already done the work, the plaster has set and now you want it flat and level with the existing. Scraping it with a trowel is probabaly as good a way as any. Now if you haven't done this or the next time use a 1 X 4 6' long or so or shorter if the patch is smaller and screed across the existing with that before the plaster has set. take off the high spots and then add more material and fill in the low spots until the wall si straight and flat. You can use the same thing to check for straightness in the set plaster too. Now to make a joining with the old and new plaster Try to shave everything flush with the existing then use your trowel to add the joint compound you are using for a top coat. Ride hard on the old work so you don't add anymore there and let the trowel feed the new work a little so you get it smooth.

Sand, touch up, prime and paint. This isn't how a plasterer would do it but it is a pretty good way for an amateur to do a repair. The best plaster for work like this in the future is gypsum plaster mixed with sand like RedTop Plaster by USG or Two Way Hard Wall by Gold Bond. A close second choice would be Structolite or Gypsolite by the same companies respectively. That is closest to what is there now.