My advice is: turn off EVERYTHING.

I did the same with ZOOM G1 Four, and after a month of really hard work I found out, that the best solution is to use Marshall as a FRFR monitor (using only Volume and Master pots) and create your sound with amps and cabinets form multi. Having access to third party IR's gives you an unlimited possibility to create the sound that fits your personal preferences.

If you use a looper put it between multi and Marshall.