The guy on YouTube using the towels must have money to burn when he mentions casting for two days solid.

Get a metal scraper and just add more plaster to your mix and scrape the moulds instead, 100% cheaper and less messing about with towels.

I mix in plastic cups with no problems (using a plastic spatula).

40,45,54,60,65,70,71,73,74,75,77,85,203,210,220,240,250,260,281,282,701