I don't think it's worth the trouble compressing springs with the struts still in the car. You should be able to remove the whole assembly easily (you've already done it, so you know what to do). I'm not even sure why anyone would use spring compressors as pictures above, unless the spring just needed to be moved around/realigned in the perches.
If you don't have enough room to remove the assembly, you can disconnect the endlinks and push down on the wheel hub to lower it and make more room. When re-installing it back, I like to get the tophat studs into their holes first, loosely secure them with the nuts (don't tighten all the way), then use a bottle jack under the hub to raise/lower it to get the strut bolt holes aligned. After doing it a few dozen times (lol) I have it down pretty good.
Stan