It's a good thing I'm not a neat freak. I have been playing with my hydracal (plaster gypsum) today in my teeny tiny laundry room. I was able to sand a decent amount of my Tech Support wire globe logo with the Dremel. Then I brushed a new layer of plaster over it trying to make it nice and smooth. Well, it sure looked nice when it was wet but now brush strokes are severely showing.
I'm going to a different approach to the Fantastic 4 logo as well. I had let some of the plaster harden in the bottom of the bucket I used last time. I was able to pop it out with some muscle. The only thing is the bottom had typical manufacturing divots in it so it's not a plain circular surface. I just tried brushing a new layer on but it wouldn't sufficiently stick to the smooth surface -- probably because I didn't sand it first. Oh well. Live and learn.