You misread the FAQ. The full sequence from the Sol example is this:
c.S 8 2D 236K(1-hit) RC ...
You can only install a jump on moves that are jump-cancelable, from the example, that would be Sol's close slash.
c.S 8 2D - close slash is canceled into a jump, but before you leave the ground you gatlinged in to a sweep. That's the entire Jump Install squence.
Now to take advantage of your Jump Install:
c.S 8 2D 236K(1-hit) RC ...
cancel your sweep in to a Bandit Revolver, then romancancel the Bandit Revolver while still in the air, you can now double jump or airdash when normally you would not be able to.
k8H and K8H mean the samething?
Here's a quick Johnny example.
KH>DBT>DB(frc) - After the frc you can not double jump or air dash.
Now try
K8H>DBT>DB(frc) - after the frc you CAN double jump or airdash
even easier Johnny example.
Kc.S>superjump - you can not double jump
K8c.S>superjump - after the superjump you can double jump!