You don't. B moves cannot be l-cancelled, but with falco's lasers, when you hit the ground, the animation cancels by itself. You get the typical 4-frame landing animation.Yes, except I don't think you need to l-cancel it.
This is how I do it as well. The reason it is hard is because you actually can't up-smash out of shield. The reason it works is because you can up-smash out of your jumping animation (jumpsquat animation), and you can jump out of your shield. The way to up-smash out of your shield is: jump, then up-smash before you leave the ground.If you just press up+A OoS you get a grab, I've read you can hit up on the c-stick twice, but that seems ridiculous to me. I just press up on the control stick and c-stick in quick succession. Up on the control stick to jump, then up on the c-stick to cancel your jumpsquat into an usmash.
I don't think it is different in Brawl, but I don't know for sure. What's said here is correct. You just have to let go of the jump button before you leave the ground (during the jumpsquat animation which is the same animation you are up-smashing out of in the above scenario). In melee at least, it doesn't matter how far you press the button down.No, it does not have 2 sensors. (to my knowledge) How short hopping works: You press jump, if you release jump before you're airborn (while still in jumpsquat animation) then you short hop. If you release it after you're airborn (after your jumpsquat animation...) then you'll fullhop. The length of jumpsquat animation depends on the character. E.g., Fox & Sheik's jumpsquat is 3 frames, where as Ganon's is 6.
It's notable that each character has a specific amount of time spent in jumpsquat (though most of the characters share the amount of time with a lot of other characters). If you are having trouble with all of this, try it with someone like Link or Bowser first. Link's jumpsquat is 7 frames and Bowsers is 9. Most of the characters have 4 or 5 frames of jumpsquat (less that 0.1 seconds!) so you have to be pretty quick. It becomes very natural after lots of practice.