Thank you for your inquiry. When working with setting type joint compounds you must make sure your tools and equipment are clean. Any hardened joint compound acts as an accelerator and speeds up the setting time. Always use clean drinkable water and be sure you are adding the powder to the water. Use the correct water ratio. If you are not mixing the entire bag use approximately 3/4 to 1 cup of water for every three cups of powder. The shelf life of Easy Sand is 1 year from the production date stamped on the bag. Product that is past the expiration date will have altered set times. Hope this helps.
Yes I use it for all my surfaces
Go with 45 minute. Don't mix more than you can use in 30 minutes
The question really is not legitimate, blocking drywall? Is not done with compound, it is done with wood blocking to support it!
You could use the Easy Sand 45, it is great to do skim coating as well as patching holes in walls. You would want to mix a small amount first a few times just to get a feel for applying the skim coat on the wall. It will dry harder that the Plus 3 and last much better with less cracking! You want to add enough water to get it to a peanut butter consistency, not too wet or dry. Done right you will get 25-30 minutes of working time. Thus mix small batch o get a feel for the skim coat. My contractor friend when doing it ads a drop or two of dish washing soap to make it flow smoother on the trowel. I have done that and it does make it more smoother troweling of the wall. After you get a feel mix bigger batches of the mix, Thin coats not real thick! Good luck hope this helps!
A good quality primer can be used on sheet rock. Kilzs is one of the best but there are many out there. I personally recommend TWO coats of primer, more work but better finish!
I would recommend cement board to do this with a good concrete mortar to seal the seams. Then you can glue the panels from the bathroom shower in place
Skim over the joints with light mud using a mud knife larger than the existing area. About a 12" mud knife. get 150 grit drywall sandpaper & sand the edges. Fire the contractor.
Unused in a cool dry place should last for a few months.