I took a look at the book I had, Compleat Anachronist No. 108, Fingerloop Braids, but could not find any directions for 6 strand braids (and only one for 6-"bowe" braids that I didn't understand).
So I went back to my sample piece and my challah-dough directions, and tried again. I think I'm getting the hang of it; I just need to take things slower. After I prove to myself that I can braid a reasonable length without screwing up noticeably, I think I'll cut a set of pieces long enough to make a braid to go entirely down one of the dress sides and try braiding it.
I also think that I'll weight down each of the string ends with a bead or something like that. One of the toughest parts to this is keeping track of which string is which after they've stuck together farther down than where the braid is forming.