I was experimenting with the burn channel last time i played, and I actually found a fantastic CLEAN sound that was very jangly and fender like. I was in 5 watt mode. Turn gain all the way off, and max the volume. Treble & Bass @ 1:30-3:00, mid and contour off. Very carefully bring the gain up a hair @ a time before it starts distorting. I couldn't believe how sweet the tone was! It was great for messing around, but I don't think I could get the tone I need for grit from the crunch channel if I was using burn for clean. I like that compressed lead tone.
As for the grit, i go for gain @ 12:00-1:00, treble @ 1:30, mids @ 11:30, bass @ 9:00-9:30. Contour @ 9:00, which acts like a lead booster that is very useful for me. These exact settings work great on blues mode too in 5 watt. I just got a Zendrive (fantastic) last weekend and I actually never left the blues channel with those settings for a number of hours. Zendrive and contour for lead, kill them both for the cleanish sounds on blues.
I should say that I'm running a Boss ME-70 in stereo, and I get a lot of my needed bass response from the solid state Fender ultimate chorus I use along side the Mesa. These settings by themselves from just the mesa are really good, but I would add a little bass to the numbers if I wasn't running in stereo.
