This is pretty much the technique I use with cotton. Weave in, split the plies in half, weave each in one direction, weave back in the opposite direction. I don’t knot the plies and I don’t split a second time. It seems to work and stay put. I leave maybe a cm end on the inside (usually it’s a sweater with only one public side). Not a county fair winning technique but my ends tend not to poke out on the RS.
I change cotton yarns the same was as for wool. Overlap the two same color yarns for a stitch or two and later weave in the ends. For a color change, I cross the two yarns and start knitting with the second color. Before I weave in the ends, I make sure the yarns are twisted and that there’s no hole on the RS of the work.