[superchevy]

You can wipe the HOK off as long as you do it pretty quickly after you have put it on the paint. I mean, within 60-90 seconds. It is a catalyzed paint, and will "eat into" the painted surface. That's one reason it sticks so well. If you wipe it off after a longer time, it will leave a "shadow" of the stripe/design where it was applied.
Don't even try to wipe it off fresh paint, i.e. painted that day.
As far as learning with HOK, it requires you to work much faster as it dries very quickly depending on the reducer you use. There are occasions where I will be doing a design, and you can actually see the paint drying on the brush and starting to skip.
I would practice with 1-shot until you get the speed and skill to use HOK.
Later,
SC