I had a hell of a time with my Mitsubishi 3 zone. I finally realized that the electrical connections on the compressor were:
1 - 2 - 3
but the line ports were
3
2
1
So I had wires for 3 crossed with the lines for 1 and vice versa. That is when I learned I could use the compressor to pump the freon out of the line set back into the compressor coils. There is a solenoid for every port on the compressor manifold which syncs with which interior unit is on... and getting freon.
I vacuumed the lines then pressurized them with Nitrogen and let them sit for a day. Of course after that I vacuumed again and released the refrigerant. I forget the nitrogen pressure I used for testing... but, yeah, it was up there. There is some "nyloc" or something sealant that I used on the flares... just the flared surfaces, not the flare nuts and not the outside of the flare that touches the nut.
The quality/expensive yellow jacket flaring tool was worth every penny!
I just used a quality set of Yellow Jacket gauges. I didn't buy the expensive electronic micron vacuum gauge. I think I ran the vacuum pump for a couple of hours just to be sure.