Stuart Noble coughed up some electrons that declared:

I use a long handled scraper (the Stanley knife type)to skim gunk off
plaster. You need to keep turning it over to keep a sharp edge, and
wiping it clean, but it beats the hell out of washing. It also gets rid
of any gritty bits and leaves you with a baby's bum surface.

Good call Stuart!

I got one of the Harris "Throat Slasher" ones with a 3" blade. It did what
you said - nearly all the paste comes off in one scrape and a quick wash
off leaves a nice surface. I use mine in a "drag" mode at about 45 degrees
inclination after a quick steam.

The other advantage is it takes the gloss off any paint too

Also handy in "push" mode for trimming off ridges of paint where shelves and
stuff used to be

Cheers

Tim