I’ve used the basic compressor on struts and rear struts (small springs). I was always careful when tightening, not going too fast and compressing each side evenly. Thing is for me, it takes a while to get the job done. I have that clamshell compressor but it’s too large for the small struts on Minis.
I was considering the Branick, but the cost is high if I’m not doing a lot of them. I’m now looking at that Jack Tech linked above. It’s not bad and I’ll likely do more struts with a tool like that.
I have been installing ready struts the past few times, but I think I’d rather start putting in quality parts going forward. I’m having to look at replacing the struts on the Charger, and I prefer to go with TRW or Sachs vs FCS or similar. Same with the Mini. I’d like to install Sachs or Bilstein in it if I’m going to hang onto it for a while.