M/S processing has been the biggest improvement to my mixing and mastering. I use it primarily to ensure that the bass is centered more and the highs (esp. reverb tails) stay wide.
The technique I found is that at the end of my chain I have devices that let me check the sound as mono, and at decreasing widths from full stereo down to mono. I listen to hear if the feel of the bass sounds the same when full stereo and when mono. Then I check at various narrower widths. That same end device also has a small cube reference speaker emulation (two of them, really), and I can test the sound that way too.
Amazingly, once I started to do this, I found I stopped using bus compression (at most only a touch), and found no need to widen the stereo field: This approach gives a “natural” feel to the field width.
I always have a limiter at the end - though usually as another check on my final level, and it generally does nothing once things are set right. If I want master bus color - say a gentle tape distortion - that goes at the front, before the M/S processing.
I don’t use a phase meter - probably wouldn’t hurt and I imagine I could find one in Max4Live… The stereo/mono testing and decreasing the stereo width testing reveal phase issues in the bass very clearly.