It takes a while to control the rear brake and release the back wheel just for the pedal kick, then block it straight
away to avoid a crash on your back. Start on a flat ground, lift the front wheel by just kicking firmly once in your driving pedal and leaning back,
then pull the rear brake when you reach a standing position. From that position on the rear wheel, let the front wheel drop a little bit by leaning forward,
and before it touches the ground, release briefly the brakes and give another kick in your driving pedal (then brakes full on again). Of course, each time,
you need to re-adjust your pedal position so that you are ready to kick with your good foot.
..Just practice...and practice and practice, until you can do at least two or three pedal kicks in a row.
Once you get there, try to be more precise with your kicks. Find some marks on the ground, and try to control where you start, and where you stop. You'll notice that if you lean forward just before the pedal kick, you'll be able to reach the next stop further. Lowering the front wheel before the pedal kick gives you more power and also compensates for the front wheel lift you get from the kick, preventing stupid crashes on your back. You can also boost your pedal kick with the bouncing effect of the rear tyre (low pressure). Then you can launch these pedal kicks one step down from a kerb and then up that same kerb to feel the move. For the upward move, you need to pull up further on the bars after the pedal kick. Make sure you control your stops before moving to bigger gaps.
Thrust your hips forward
By thrusting your hips forward (your center of gravity pretty much) on top of each pedal kick, you are building the momentum you need to truly move forward with the bike during the hop. Else, just a pedal kick with no momentum will send the bike very vertical in front of you, and you won't be able to hold the balance. For bigger gaps, you must synchronise the mechanical kick that rotates the wheel, with the thrust of your hips forward. Then, from the top of the pedals, finish or extend the kick with an extra flex from the ankles (it's all the same move but optimised further through the ankles). For this to work well, you must position your feet well back on the pedals (to push with the ball, not on the middle of your foot).