I’ve already worked all continents but never requested the WAC certificate before. The main reason for this is that you can’t apply with LoTW credits. You need to have paper QSL. Via the DARC Contest Logbook however, had the possibility to import both eSQL (AG) and LoTW credits and you can apply for the certificate over there. For free, as it will be delivered as PDF. How nice!
So, I figured out (after) to got WAC with QSL cards that you can do it with just LoTW. The process is documented here: http://www.arrl.org/files/file/DXCC/WAC%20and%20lotww_pdf_20141.pdf
It’s a little convoluted, and if you read the WAC application it sounds like you can’t, but it’s possible (but not free like how you did it).