Some tools we use every day.:
Water level for bag positioning and level.
Various sizes of levels.
Water leveling gauge
Water leveling gauges work very well. We placed ours on a large base so that it is a one man operation. Also a larger surface area for foundation stone levelling. Used extensively for foundation levelling, bag setting and a host of other things. Fantastic tool.
Made from gate hardware and electrical pipe (stronger than the gate metal pipes). An essential tool. Used all the time.
We have used the compass for positioning various items at FF level such as the yellow stairway plinth’s and center log plinth, which supports the loft beam. (grey bucket).
The stairway layout (spiralled) was also much simplified by making use of the compass. It is being used extensively for correct bag placement.
The correct radius is checked for each bag.
Levels in two planes also. Not every bag.
Move them before they set if you have to.