Mixing plaster in a plastic bag

Let sit for a minute or two, then stir for about 5 minutes, being careful not to entrail air into the mixture.

I’m not a plaster master, so I don’t know if this is a good or even original idea.  By mixing plaster in a plastic bag, it seems easier to remove bubbles from the mixture, while pouring is much more controlled.  It’s the same idea as using a garden watering can for pouring glaze:  You pour from the bottom where pressure is highest and bubbles are fewest.