Nice video.
Double declutching is simple once you get the hang off it. It's just a case of thinking ahead all the time. Anticipating when there are bends in the road and junctions coming up.
Changing up is fairly simple. Clutch down, into neutral, clutch up, clutch down into the next gear. Then clutch up again.
Changing down. Clutch down, into neutral, clutch up, blip the throttle to increase the engine speed, clutch down, change down. Then clutch up again.
So when I approach a junction I slow down using the brakes a bit, well before the junction, change down using double declutching from whatever gear I am in, then down again allowing the engine braking to do a lot of the work. Leave it in 2nd until I need to decide whether I need to come to a total stop. If I don't I leave it in second and accelerate away. If I do I then I do a quick double declutch and pop it into 1st or sometimes just stop in 2nd and pop it into 1st when stationary.
Tony