best stuff i found to use is lafarge gvylon.
depends on size of machine mine will take around 4 cube
agree with above, you can make a lot of money until the arse falls out of it as it inevatably will.but its bobing along because of the craze in under floor heating.
only thing i could tell you plasterjfe is about wet screed as i dont bother wth any other, and blones has pretty much covered it,if you pardon the pun.