I don’t have a NC but I’ve made a pretty deep study of the brake system when I was figuring out how to do a full brake bleed without one. Essentially the brake system has a few “loops” in it (called circuit A and B in the RAVE). When you do a modulator bleed it basically circulates the fluid from circuit B, which can be thought of as the ABS/TC/HDC circuit in to circuit A, which can be thought of as the “regular braking” circuit. So that being said, you have to bleed the modulator circuit before doing a power bleed on the brakes, so any bad fluid/air from the modulator is flushed in to circuit A which in turn is flushed out during the power bleed to the individual brakes. The proper sequence as I can work out is this:
1) A traditional (or power) brake bleed as you would any other car. This gets fresh fluid from the master cylinder to the WABCO unit.
2) A “modulator bleed” with a NC or by doing a few activations of the HDC (this is what I do). This sucks in the fresh fluid from your first bleed and displaces the old fluid/air in the modulator out to the main brake lines.
3) A traditional (or power) bleed again to remove the displaced fluid from the modulator (which is now in your main brake lines) out of the system.

I did this procedure last week and my brakes feel better than ever. I know the “double bleed” is a real pain if you don’t have a NC but it’s worth it, not only for your own safety but the brakes are in integral part of the trucks 4WD system as well and I want that working well too!