CJ / Dirk,
I did both. I think it depends on the timing. If it is in the middle of a restoration and is high up with no engine installed that is one thing. Mine was just raised on axle stands. I think the 10mm threaded rods are essential for safety.
What I found is that the compression tool bought me enough room to safely get the springs and rods installed. Once this was done I tightened up the nuts on the rods to take up the slack. I then removed the compression tool and finished the job using the nuts on the threaded rods.
It took me a few attempts to optimise the position of the plates in the spring to make sure they compressed it enough and I could still get them out when the spring was fitted.