rare than among indies.  Indies that are compatible for doubles just need to agree to work together and can easily arrange their transportation to each other for sessions, but in the Kgirl scene, two girls have to be willing to work doubles together AND be working out of the same location.  The girls don't get to pick their location, so it is often the luck of the draw on rooming with a girl that can be a doubles partner.  With that said, if you watch the CV ads, there are usually a few Kgirls popping up each month that will offer doubles sessions in the body of their ad.  Also check the TER reviews for Asian girls each day for new doubles partners popping up in reviews.