if you watch that video esp the slow motion view from the front,
the rider is using the front brake as part of the technique..
also note when he extends his fingers over the brake lever,
and when he retracts the fingers back to the bar/throttle..
in my experience with 5 [now] road hondas, engine braking
is part of riding the motorcycle, simple as that..
my 250, 450, two 750/4's were ridden daily and on weekends
including fairly hard at times, and all just got better with age..
i was a bit obsessive with oil changes, perhaps, but if there was
some serious damage potential from 'normal' engine braking
then my hondas didnt suffer from it..
thats not to say i never used the throttle when downshifting,
but as i recall this would be part of quite high speed riding,
not typical suburban riding and average type riding..
you dont want to cause your rear wheel to jam up its and thus
the drivetrain and engines normal range of function..
thus matching engine, gears and wheel rotation could be
helped by using this sort of technique..
but mate, if youre having trouble learning it, as you say,
then in the real world and generally rational riding habits
its not something to get your balls in a knot about [
if you find yourself changing down esp the lower gears
and revs screaming upwards and/or tyres screeching,
then it might be time to start thinking about how this
is happening and what you can do about it in your
riding habits.. otherwise, keep practicing somewhere
safe, and like anything, you will get better at it..
just separate in your mind normal road riding from
wringing everything out of the motorcycle such
as in racing type scenarios,, and enjoy
whatever riding you are doing...