Spraypercrete is a good system. You'll want to wear a raincoat and a full face mask because you WILL get splashed. And keep your mouth closed :)
I fill the drum with loose dry paper. The drum has 3/8" holes every 3" or so around the side at the bottom, for drainage. It really does not drain much even with the holes. Another drum has a 12" gate valve on it for dumping from a platform. I start spraying, moving the spray wand around. Curtis always swore by rotating nozzles, and I'll bet that would be faster, but even a non-rotating nozzle does fine. As I spray and pulp starts filling the drum, the level drops as more paper is pulped. Then the level comes back up as the paper is fluffed by the spray. I am constantly moving the nozzle, and as the barrel starts to fill I move up and down, "feeling" with the wand for lumps near the bottom. When the drum is about 3/4 full of pulp I add in portland cement. The amount of cement varies depending on the final use of the papercrete. For just fill, I use very little cement. For structural things I use more, up to 10# in a drum. At this point I have a method of putting the spray nozzle under the little floating island of cement, and using the spray to suck it under. That way I don't get dust clouds to breath, and all that waste.
By the time the drum is full, the cement should be thoroughly mixed in. You'll know the paper is properly pulped by looking at it. Feeling around in the mix with the wand will tell you if you still have lumps. A little experience will show you how much paper to start with, and you can always add more paper as you are mixing, if you didn't get enough. If your mix is too thick and lumpy, you can scoop some out and save it for the next batch, and finish pulping with less paper.
At this point you should be able to pump the mix. Sometimes I bucket it out onto a wire mesh drying table to drain, for hand application like plaster. Other times I have just pushed the drum over, letting the pc hit the sand. A few minutes of draining, and it is ready to scoop up and use.
I have tried various formulas over the years. Cement of course, otherwise it wouldn't be 'crete'. Some people use lime for part of all of the cement. Some add pozzolans or flyash. I used to add borax to repel insects and mold, but I don't have a problem with either so that was not needed. I have never been one to put dirt or sand in the mix. I'm after insulation, not thermal mass. I think every papercreter develops his/her own formula that works best for the conditions. I would bet if someone did thorough testing they would find that most of the formulas are similar.
I have been living in the dome shown at that link for several years now. I have not yet finished the top half, it is only about 4" thick with the panels and a little sealing coat. The bottom seven feet or so is slipformed over 12" thick. I will eventually finish the top half, when I get tuits. So far it isn't a priority, I have been comfortable.
Here is another method, using cellulose insulation. While this works, I don't necessarily recommend it. The idea was to use bottles to fill space, leaving air voids and reducing the amount of papercrete. Mixing is easy, and the bottles work fine as filler, especially the ones that are totally encased. Without doing any testing, I feel that this papercrete is not as strong as "normal" pc. After the panels have been out in the weather for a year, there is no apparent deterioration, and testing might show that there is little difference other than cost. Cellulose insulation is not cheap.
https://www.youtube.com/watch?v=CbBxpDTFduc 
