I have worked with cement not plaster. And grouted out the inside of many in-ground pools. Using a trowel is an ART. IT takes a lot of practice to become GOOD. It takes years to be a master craftman with a trowel. But the other Joe says I don't know what I'm talking about. If you know it all, then why are you asking the question? Sorry, I didn't give the answer you wanted to hear. OK, I'll start over with the answer you want to hear. "Its a piece of cake. Just slap on the plaster and trowel! Nothing to it. My niece could do it!" Hope that's the answer you're looking for.