I dedicated some time to it, and I figured it out
although there was some swearing and some frogging involved along the way.
Purling two handed for intarsia (or fair isle with more than two stitches of each colour) does work just like Philosopher's wool way of knitting, but because of the way you hold the yarns when you are purling, you have to pay attention to which yarn is held where.
If I was video-savvy I'd youtube it. But I'm not.
BUT... if anyone ever wants to know how to do it, just ask