there are lots of ways--(besides the 3 i've outlined in my tutorial)
you can do a double I-cord cast on,
or a magic (or turkish) and knit a few rounds(solid color) then add second color and have a solid cuff--
you can use the magic cast on using 2 yarns,(2 colors) (and start working double knitting almost immediately)
for both these methods, you hold the two needles together (3 needle bind off style--and knit them onto one needle--either after a few rows (solid cuff) or immediately (2 color magic cast on)
There are several double knitting techniques.. (simple, 1 inside the other (as in socks) 2 color interlocking (jacquard)---
(all called "double knitting"--and the best method for casting on depends on which style of double knitting you are doing!