These days, I apply one coat with the foam brush, let it cure for a few hours, sand it with fine grit sand paper, and then repeat that process with another coat or two of polycrylic. Since you've already done the polycrylic coat, I would just go sand it and add your next coat ...
If cost is a consideration there are less expensive tools available that will do the job. One other thing the video showed them putting down Red Roisin paper and referred to it as a Vapor barrier. It is not a vapor barrier. You want to use something like Aquabar...
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