I do both ways. Always use the clutch for 1-2 and downshifts, and use the 2 finger flick the lever, throttle, and shift at the same time for most upshifts. Except for 6th gear, which will just about only go in if you don't use the clutch.
Also, with a passenger, not using the clutch on upshifts keeps the helmet banging to a minimum.
Also, with a passenger, not using the clutch on upshifts keeps the helmet banging to a minimum.