Generally speaking when we're Calibrating it's done VFR, it allows us to self-position more quickly than being IFR and vectored, it also gives us more flexibility in holding / manouevering and allows air traffic to apply VFR separation with us.
As for the crewing thing, our B200's are "single-pilot" aircraft but we are required to operate 2 crew on precision calibration tasks. There is a lot going on during a calibration with both front-end guys busy looking out, flying, navigating, liasing with air-traffic, co-ordinating with our rear-end NavAid Inspector and of course looking out again! (Hopefully)
Personally i'd be very happy if ALL aircraft (including microlights, balloons and gliders) were required to carry at least Mode 3 A/C transponders and if all aircraft involved in our kind of operation were required to carry TCAS. At present we have a TCAD system which is a lot better than nothing but still not really good enough.