The principles of a ribbing cast on is always the same for Japanese machines:
1. Arrange needles for your desired rib.
2. Knit 1 zigzag row (set both beds to knit). Hang cast on comb and weights symmetrically.
3. Knit 2-3 circular rows - this means set the main bed to slip left and the ribber to slip right (or the other way around, as long as one carriage slips in the opposite direction to the other).
4. Knit another row with both beds set to knit - this is row 1.
There is also a step 1.5 and 3.5 which are not always necessary:
1.5. If you want to do a 2x2 rib, or any rib that has two or more stitches on the main or ribber bed together, you set the needles up first and then rack 1.5 positions before the zigzag row so that the needles are arranged KPKPKP (knit purl etc) - you cannot start with KKPPKKPP as it will not work - on the next pass KK and PP will become one great big stitch, and disaster will ensue! You may have to add a stitch at one or both ends to keep the alternating pattern consistent.
3.5: Rack back again to the original position. If you added any end stitches at step 1.5, now is the time to decrease them again.
NB: to do a wide rib such as 5x5 you would have to rack a LOT of positions to make this work, and the yarn would probably not stretch enough to make it possible to rack back when you get to step 3.5. In this case, it's better to do steps 1-3 for 1x1 rib and then transfer your stitches between beds for your desired rib. The selvedge (circular) rows will barely be visible in the finished welt.
Edit 30-09-2013: See also Ribbing cast on cheat sheet for sketches comparing Brother to Knitmaster