I did end up just buying the Bain scarf pattern, and reading how it is done for her big celtic knot pattern. While it seems complicated, I figured it would be nice to share the basic crossings, in case someone else finds the thread and wants the technique, with the hope that expanding into others is intuitive. (As for getting these done right in intarsia, as was my original plan for learning the technique, that may need work.)
Instead of X-wide cables being simply kX on a a reverse stockinette background, an X-wide cable becomes kX, sX wyif, on a reverse garter background. As you move along, the paired knits and slips tend to draw together as a double layer. Crossings also take more rows to be done, with traveling over the background taking 2 rows and over another cable taking 4.
When traveling over the background, on side 1, you have to pass the background stitches between the kX, sX set, and then on side 2, move the background again to complete the crossing. For example,
2 wide cable left 1
CO 8 stitches, (2 background on each side)
Setup rows: p2, k2,s2 wyif, p2
Repeat the setup for however long is desired, this just makes the cable go straight up the work.
Row 1: p2, s2 to cn-front, s2 wyif, p1, k2 from cn, p1
Row 2: p1, k2, s1 to cn-front, s2 wyif, p1 from cn, p2
When crossing the cables over each other it is more complicated. Starting with them right next to each other, i.e. kX, sX wyif, kX, sX wyif on the previous row. Row 1, twist the central 2X stitches. Row 2 and 3, twist the first set of 2X stitches on that side, and Row 4, twist the central ones again, all the while minding the facing of the twisting. For example,
2 wide over 2 wide, Right Passing
CO 12 stitches (2 background on each side)
Setup rows: p2, k2, s2 wyif, k2, s2 wyif, p2
Row 1: p2, k2, s2 to cn-Back, k2, s2 wyif from cn, s2 wyif, p2
Row 3&4: p2, s2 to cn-Back, k2, k2 from cn, s4, p2
Row 4: p2, k2, s2 to cn-Front, s2 wyif, k2 from cn, s2 wyif, p2.
On these while learning, I would recommend grabbing some stitch markers or paper, and doing the swaps just on the table to get a feel of what is wanted, because when your stitches are all the sane color and a bit hard to read, it is easy to get lost.