I had to set the Send to 100 and Return to 180 to make sure the Bugera wasn't attenuating the signal too much before it came back into the GT-10. Was it similar with the 5150, Markus? I use the Output on the GT-10 as a master volume anyway and that seems to work fine.
I also set the assigns on the volume pedals so that when it is fully heel-down and 'silent', the tuner comes on - useful for tuning up between songs or quiet sections. However, it's not truly 'silent' for me, and I think that's the fault of the amp being not entirely wired in serial (although how that is possible, I have no idea).
Also, another 'trick' I just remembered: I try not to change patches during a song as the patch change time is just too slow and noticeable. So I usually have Ctl-1 and Ctl-2 set to switch several things at once (eg. I have one patch where Ctl-2 adds EQ, reverb, chorus, and delay, to change a rhythm sound into a lead sound), and can also use the Channel A/B switching to go through very different configurations with no latency.