I don't have P21S but I think I read that it can be used both ways. I read that it is very easy to wipe off even letting it haze...? Maybe others that have it can feedback on it. I am considering the P21S too. Do let us know on it, Rsurfer if u have applied it later. Thks.
But I usually WOWO with paste waxes coz I dislike to wipe off after letting it haze. As it's a bit difficult compare to sealants....
It says on the can to do one panel at a time a to NOT let it fully haze before removal. So, I would say that the best way to use it would be to WOWA on each panel. I have always done it this way I I get perfect results.