Sounds like you have all the advice you could need. This was massively frustrating to me in the first season with my Enfield.
-Second the notion of having a good boot, with a firm toe to help you get that gear up.
-I don't "lift my foot" to shift, I lift my whole leg. That helps, mostly to not be lazy.
-Someone suggested here that leaving the shifter up until you have released the clutch helps. I think, again, it's just to reinforce a purposeful shift.
I was missing a lot shifting DOWN when entering corners quickly. That SUCKS when you miss. Doing the clutch lever in trick seemed to help with that.