On the bucket is says mix and apply before adding water. Videos are kak. I'm a trade qualified plasterer blh blah experience etc. What I do is read. Read the bucket, read the data sheets, read books about plaster publishd by plaster companies, read summaries and technical analysis of arbitration processes where products have failed.
So fresh bucket off the shelf : fine
Fresh bucket mixed with 500W drill : Perfect
Apparently some companies put less water in the premix over winter to avoid freezing during shipping, which may have an element of truth to it. At any rate the general rule of thumb is that you can add about a cup of water to a 5 galon pail of premix without killing it. Too much water and it becomes what you call friable, what this means is that the paint wont bond to the compound, so you have what l9oks like paint faliure, but its the premix. When you dilute anything you spread all the parts out, then when the water has evaporated all those parts are too far from each other to create a strong matrix.
If its dry bagged it should say on the bag how much water per bag, like I think a 20lb bag of Sheetrock Easysand says something like 5.4-7.1 litres dont quote me on that, but its on the bag so you just use maths and say use quarter of the water for quater of the bag. With drymix the less water end of the spectrum is stronger so good for filling, the more water within guidelines is still strong enough but easier work for second coating.
Your choice of materials depends largely on your climate. Hot dry climate use premix. Cold or humid climate use dry bag.
So yeah I know this is an old thread, but this is something of a PSA too. I like to hunt down weird questions about plaster and give informed answers to prevent the future generations from messing up their job. You could think of me as a whitehat plaster troll if you wanted, or you could just learn to use google better by taking data from packaging and using keywords like data as in technical data sheet. Any industry has its own members associations, publications, forums - it doesn't matter if it's plaster or gasoline, reading will get you further than 99.9% of videos out there... unless you already know the rules and are looking for new ways to break them.