Hi
Having done plastering and got plenty on the floor over the years, I found the best way to get it off was to make it damp slighty with a mop and leave it for a bit. Then use a blunt scraper carefully and it then comes off with a little effort as it seems to break up due to the wetting. Any persistant bits just keep at it and use a damp cloth to polish off any smears.
Worst plaster of all is the bonding as that sticks like s**t to a blanket but comes up in the end with effort.
Good luck,
Steve