Lifting the rear end off the ground also works. Setting the drive chain on the loose side (just barely touching the chain) also helped.
Make sure your idle speed is set within spec. If it's faster or if trying to shift it while it's at fast idle warmup, it's worse.
One thing I'm experimenting with is Lucas oil additive. It's really slick and makes the oil tacky. Added a bit to the gearcase oil (75w90 synth) and seems to help the dog gears slide better against each other when shifting.
Careful with the Lucas stuff, it's probably less of an issue in a non-pumped lubrication system but it has a reputation for diluting the anti-foaming additives in the oil. Air doesn't lubricate as well as oil so...