I have made plaster cloth out of used dryer sheets, a good quality paper towel could work too.
For a plaster avoid ready mix joint compound as it dries by evaporation and is realatively weak. I like using USG 210 minute Easy Sand dry mix setting type joint compound. If you want a quicker set up time go with the 90 minute.
I mix it pretty soupy for making my own plaster cloth.
The plaster and grout you already have, there are so many types, just mix some up and make some thin "patties". Once dry try to break them and see what you think as far as their strength.
