Hey RG, it's an interesting journey
. Mike was talking about the front boost (extra layer) last night. He's looking to try something in front (based partly on your comments). IIRC the main tweaking I ended up doing at rehearsal was more about getting the master vol settings right so I could solo over the other guitar (not as big an issue for you). These days I use the MXC CC pedal to control master vol on the MP2 and tend to use the same patch for 95% of the time. With the MP1 I had to get the volume changes right in each patch.
Hey Richard, I'll actually do a demo clip of "the extra layer" To demonstrate my point with lots of gain right! Lots of gain, but then I'll dial it back a good bit till it's lighter gain, but then I'll throw in the boost for the extra layer

It's something I used to do back in the day before I understood anything, an basically I achieved the same sort of thing with a wha in stuck position of choice. That also added the thickness I was after.
As for Mike, well the only thing I can say is, if you throw a clean boost infront you can get the extra gain sure and sounds more like the original sound. However throw a drive pedal in there and keep the setting basically on zero apart from the level you get thick as shit "extra level". Now there are a million pedals out there that can do it and of course each is going to have its own little unique flavour. Two ways I enjoy doing the boost (stock MP1 only) is through an EQ pedal set with a boost in the hi mids (basically like a trebel boost pedal which is actually hi mids - common guitar player folklore to call it a trebel boost) or else an overdrive pedal.
Basically I use the boSS gt5s analogue drive section and pick the vintage overdrive option for mine. Or the EQ module and set a boost from about 1k or where ever sounds nice and then turn the output volume up to suit the amount of gain I want to generate. 9 outta 10 times I just use the vintage overdrive set at zero and output level set at 50 (halfway).
I've heard of many using a tube screamer and MXR over drives to act as their boost for the MP1.
As for master volume. I have no issues setting levels, trained myself early on to work at that kinda thing. to match patches levels. Then use the output knob to match to the levels say with patches on the MFX so hey had the same output and then I could switch between either.