I made a lot of fiber filled cloth birds for ornaments. I gave them thorns for beaks, and used old wire for the hangers and little feet. I've used plaster before a little, and I like the look.
So here's what I have learned about using plaster over cloth:
if you have many things to cover at the same time, mix a small amount of plaster-it gets hard fast.
The bird above has a very wet mix covering the cloth. This takes longer to dry, and seems to make a smooth covering.
When the plaster is a little dry, take a wet cloth and wipe off stuff not wanted. Plaster dust is not good to breathe.
It may have been better to wet the cloth before applying the plaster, but I put it on the cloth dry. I used a rubber glove, but I did get plaster on my hands-but I cleaned it off quickly.
Do not ever rinse containers or wet plaster in your sinks-you'll have clogged drains. I used old dairy containers and cleaned them outside with a hose.
These are going to be Christmas ornaments, so I'm going to experiment with different methods of decorating the plaster. I'll post about that later...