I'm in the process of a large plaster-and-lath removal; my methods have evolved over the course of the project, maybe these tips will help others who find this question.
I found that it's easiest to peel the lath one or two pieces at a time. Pull it with a pry bar or crowbar exactly where it's nailed to the joist (in my case this meant four places), and then pull down the wood piece itself and set it aside. The plaster will bend as you're bending the wood; it will peel off the ceiling and fall to the floor. You can then shovel the plaster into containers and cart to a dumpster, e.g. The hardest part of this process is getting a line started: it takes some digging with a pry bar to get your first piece. Once you get going it goes quickly.
It's easy and very effective to just smash everything down but then you have a big mess: the lath won't cooperate with bagging or shoveling and so has to be picked out. Maybe this is my OCD but I bundled most of mine and posted it to Craigslist and it was gone over the weekend--evidently some DIYers are doing the opposite of you and me.
I didn't find an effective way to keep the dust out of the air, instead just wore a respirator. I found that the plaster dust dries out the eyes too. The hose method you mention might be worth trying.
A few other tips:
- This will be obvious but don't expect to be able to carry a big contractor bag full of plaster; a 5-gallon (e.g. homer) bucket holds about 30 lbs.
- My plaster varied in quality: some finer porcelain-like plaster would not admit bending and had to be smashed down.
- I did not have the opportunity to remove floorboards above but when demolishing from the other side of a wall, yes it's easier to simply punch out the lath close to the joists, so that the line of nails squeaks out in unison. I would estimate that it cuts the time in three.