What am I talking about? I
do too know how to get ko-soto while advancing. Doy...
Now ko-soto advancing, for me, seems to be something I pick up as a follow up to o-soto. Then again, I haven't played with advancing ko-soto on it's own, really, but since I've been thinking along these lines, I'm going to start. (I get it nicely while going backwards, though 😈 )
Here's Okano's entry, which is a little different-er than mine, but it's interesting to look at. I'm not sure why he does two "taps" with his foot (one to each of uke's feet). He does a deep step with his right foot (the sort of x+1 idea that Kyle talks about), then does a quick exchange of feet (as in kouchi), tilts the guy's posture to that back corner and does his little foot tap.
I, on the other hand, have just been stepping deep, but I'll step deep with my right foot over to uke's right foot (which means my right foot crosses my body to a degree, which may be a bad thing, I don't know), tilt the posture, and sweep with the left foot. So far, it's taken most folks by suprise...