In article , Bill wrote:
I purchased a 25# bag of Durabond 90 today.

Take it back and exchange it for a bag of EasySand 90. :-)

1. Can I mix it in a plastic bucket (package says it gets "very hot")?

Yes. It gets warm, but not nearly hot enough to melt the bucket. If you don't
mix it all at once, put the remainder into an air-tight container if you want
to be able to use it later. The stuff cures by a chemical reaction with the
added water; the same reaction occurs (albeit at a slower pace) with
atmospheric moisture. With the humidity we've been experiencing lately, I
wouldn't expect the shelf life of an opened package to be more than two or
three days.

2. If I apply it with tape, would I generally add more tape if I add
setting compound later?

No.
[...]

Aside from cleaning up around a couple of my electrical boxes, my "most
troubling" joint will probably be the one about 3 inches from the
ceiling, running the length of the walls, where my old and new drywall meet.

You *definitely* want EasySand, not Durabond, for that.

BTW, There are lots of warnings on the package of Durabond 90 about the
risks of the "dust" from sanding it.

That says a lot more about the legal profession than it says about the dangers
of the product. :-)

I have just a simple drywall
sanding pole. I will wear a dust mask when I sand, but should I
"hesitate" to sand Durabond under these conditions?

No, not at all. It *may* be dangerous to someone in the trade who sands the
stuff all day, every day, without a mask. To a homeowner who does it a couple
times a year, they risk is IMO pretty near negligible.

It's a good thing I don't have to pay myself by the hour--and I'd charge
myself double for the 90+ degree days!

*My* current project is in the basement. Nyah, nyah... g