Diablo Dents- Welcome to Autopia!
Long-winded ramble on single stage paint follows:
I really like single stage ("ss") paint, in many cases (including the Guard's Red, had '78 in that) I prefer it over basecoat/clear. It just looks different/"richer" to me.
I sure wouldn't use Nu Finish on that fine car, it's a harsh product...its abrasives and cleaners are primarily responsible for the pigment transfer when you wax. Yes, it does provide protection but so do many better products.
If you get significant pigment transfer when waxing ss, it comes from: oxidized paint that should've been cleaned off before you get to the wax step; abrasives in the wax (e.g., cleaner-waxes), coarse wax application/removal media.
Generally, yeah, the paint you "lose" when working with ss should only be the oxidized "dead" paint. You remove this to expose the "healthy" good paint and then you protect that good paint with some kind of Last Step Product ("LSP", i.e., "wax").
Abrasives will *always* result in pigment transfer with ss and so will some strong chemical cleaners. Best to minimize this (so you don't run out of paint) by a) only using abrasives as needed, b) keeping the paint in good condition. Reds will always fade a bit when exposed to sunlight so in the (very) long run, it's a losing battle. Thus it pays to do everything you can to preserve the paint you have.
If you have any marring (scratches, etc.) then you need to use an abrasive polish to correct that (if desired). If you have any oxidation you can use either a mild abrasive or a chemical cleaner..one good choice that gets little attention these days is Pinnacle's Paintwork Cleansing Lotion (similar products include P21s's paint cleaner and Zymol's HD Cleanse or Meguiar's Deep Crystal step #1). A somewhat more aggressive approach would be Meguiar's #80 Speed Glaze (ignore the name) or a polish from 1Z like their Paint Polish or their MetallicPolish Wax. All the above work well on single stage (first-hand experience).
Some ss paints really benefit from an oil-rich "glaze" (e.g., Meguiar's "pure polishes" #3/#5/#7/#81/Deep Crystal step #2) after the paint is polished/cleaned. This will enrich the look of the paint and help keep it from drying out (not a problem with basecoat/clear paints, but a problem with single stage). I'd consider doing this if you use the Pinnacle or Meguiar's approach for the preceding step (the 1Z polishes leave enough oils/wax behind of their own that you don't need to do it with those IMO) but it's not mandatory.
Then you apply the LSP/wax. Lots of choices..IMO Pinnacle Souveran looks the best, Meguiar's #26 also looks good on this paint, and anything else nonabrasive/noncleaning (again, I'd ditch the Nu Finish) would be a good choice too. Collinite waxes last a long time and look better than some might think. Some people prefer synthetic sealants like Klasse or Zaino on ss paint, but I'm not one of them; I prefer carnauba-based waxes.
Cliff's Notes version w/OTC products: You could do a lot worse than Meguiar's Deep Crystal steps 1&2 topped with #26. If you have any serious scratches you'll need something more aggressive, but those three commonly available products would sure beat Nu Finish IMO.