Really do you get the same set time over concrete block?
I heard a handful of board finish slows it but i doubt that...
another guy I know plastering a lifetime swears by adding milk as the preservatives slows the set...He told me he was skimming a room
with another plasterer and he was drinking a carton of milk and he poured half of the milk into the bucket before his mate started to knock up, and he said the
gear hangs around for ever, apparently his mate swears by it now !!!