You are probably kicking it over fine enough being that you have plenty of experience. I will say however that the WR and YZ kick start technique is a bit particular compared to other bikes sometimes... especially for the older bikes. In these situations I always wish I could teleport to the persons bike and try kicking it over myself just to be sure. O.O
As I've mentioned in other threads, these bikes will flood pretty easily. SO when your kicking it over, if its been more than a good handful of tries, its possible that it is already flooding. I'll list the method I used to kick mine over just for the hell of it. I'm sure your tired of seeing this crap though
1. Turn on fuel
2. Push kick start down till you feel solid thud, its pretty obvious... well you know this already.
3. Once your at the hard spot, pull the decompression lever in and push down about another inch on the kick start.
4. Let the kick start return all the way back to the top of its stroke, make sure you have let go of the decompression lever.
5. Make sure your hand is off the throttle (I put it on the brake fluid resevoir), starting from the top of the stroke, make a good solid kick all the way through the stroke all the way down until it hits the footpeg.
6. If it doesn't start, repeat the process. If it doesn't start like this within several atttempts of good solid kicking, I would say it is definitely not your technique.
Some other thoughts: IMO these bikes really don't need the choke to start even when its cold, but the coldest I ever start my bike is around 30 degrees so yeah. They also really don't need the hot start either, if they are set up properly, they should be able to start by proper kicking technique within the first few kicks... Maybe its just my bike but it will flood really quick, like after about 8-12 kicks, if your not kicking it properly, (like when someone new is trying to start it up) it will be flooded by then. So if it appears to be flooded, turn of the gas, pull decompression lever in and kick it over about 15-20 times. then turn your fuel back on and give it another go. Also I can't say I would ever suggest twisting the throttle to prime it before hand, unless maybe its in subzero temperatures... in my experience this only leads to painful kickback and hard starting.
Just my thoughts, I hope you do get it figured out though, once you get past the headache of learning to get these bikes going they sure are fun.