I used to have one beer when I added the first hop addition.
Now, none at all, because I'm usually brewing on an empty stomach beginning around 10-11:00AM.
Having said that, one or two brews during a session would not cause nearly the problems as people standing around watching me brew. I guess this is why I don't like teaching others to brew; certainly not rank beginners.
As for hot spent grain melting plastic bags, I use the plastic grocery bags from any supermarket. They don't melt, and they're free.