I downshift frequently more for fun than need but I don't use the sophisticated techniques discussed here. I simply blip the throttle just after pushing in the clutch & before moving the shift lever.

 

when im not feeling too lazy i revmatch and downshift while braking. i've never double clutched though. i thought that is what the synchros are for, so i let them do their job.

the most rewarding experience of driving stick has been getting consistent and good at heel-toeing. it's great being able to downshift through a turn smoothly and having all the power on tap coming out of the turn.