Skip, thanks for outlining this. Hopefully now people will be able to find it in a search. The info is out there, yet so many seem to try old analog methods, and then bitch that digital can't sound as good. Or they never tried analog, and are just not exercising good gain staging, having the same poor results.
I'd like to add another (seemingly) well kept secret for getting a good ITB mix :
Analog is very forgiving and sweetening to the high end of audio. Digital (generally) not so much. Knowing how to deal with that problem is KEY to getting a good ITB mix.
Many years ago when talking with an engineer (the slide rule kind, not the faderjocky kind) who designs the stuff we use, he asked me if I would ever do a 2" analog mix on a Neve without using HPF's. I said "no, they are essential to cleaning out the mud and getting a tight and open sounding mix". He said "Good. In the same respect, you shouldn't be doing an ITB mix without using LPF's either". Same problem, opposite end of the spectrum. 180 degree problem. The buildup on a super accurate HF's, what you put in is what you get out, digital playback system is equally destructive to getting a smooth top end as LF mud is to getting a clean mix on the bottom.
As to how to do that, what to use where and where to set your LPF's, I'll leave that to your own experimenting. I can't deliver it all in a nice neat package now, can I???