After reading a plethora of post here, skidiva.com, youtube, and other sites on the intraweb thing there is a vast array of opinion on the timing.
I just stated waxing my skis this year and in trying to educate myself from and it interesting that some folks will say wait at least 20+ minutes, to no need to wait, and all in between and beyond.
My minimal understanding is that the ski technically needs enough wax to penetrate the structure/porous portion of the ski. The practice of scrapping, brushing, etc is to remove remove the excess wax and leave behind the wax the ski has absorbed.
Now from what i can gather, as one applies melted wax it starts to heat up the ski and presumably start the process of opening the structure the ski. When one starts to iron the wax /in/on this causes for the wax to then fully penetrate and saturate the structure.
Now at this point does it matter if one waits five minutes (giving the scrapee time for a refill) and scrape when the wax is starting to harden or wait 20+ minutes (or however long) and scrape when it is fully harden? Does scraping too soon 'scrape' wax that has been already absorbed by the ski, thus not allowing the ski to fully accept the necessary wax?