I can vouch for the "the tool" - ie something like the Laser Tools copy of the VAG one, I did one side (broken spring) using things like screwdriver bits but they "rise" too quickly and if you do get lucky and they open the clamp up then they do tend to annoy you by jumping out! The correct tool is far more managable and trustworthy - just remember to remove it before reclamping as it will still be in there!!
One thing that I would add to the above
guide is, do the initial slackening of the strut top<>top mounting nyloc nut, before removing anything and do the final tightening of the new nut after refitting everything - as it might save chasingthe strut around the garage floor!