Can you use the Tryphon pen polishing kit effectively on pretty much any pen? I have a Montblanc Meisterstuck and a Sailor Profit 21k, both of which appear to be made of similar materials, which are different from my other pens. (The Sailor even has that reddish coloration when I hold it up to a bright light, just like the "precious resin" of my Montblanc.) They've both have minor scratching on their barrels that I'd like to clear up.

Any suggestions?

I have used the Tryphon polish and wax with success on my Montblanc pens.

Looking at http://www.tryphon.it/catalogo.htm
seems there are 3 basic polishes;
Celluloid Polish, XP Polish
"a combination polish and scratch removal cream, very effective for a one-pass restoration of celluloid, acrylic and thermoplastic pens. Recently re-formulated from a paste to a thick liquid, it will remove light scratches from the surface of acrylic, celluloid, PVC and metal pens. It leaves the surface polished to a high gloss. Superb results even with a single application. The new bottle contains four times the amount of the old jar. Now in liquid form, more effective and easier to apply."
and Liquid Carnauba
"A new surface gloss restorer containing carnauba wax in liquid form. Perfect for gently restoring the sheen of celluloid, lucite, plastic and lacquer pens. Safe and non-reactive with most pen materials. Our carnauba wax does not cause surface build-up and does not craze. Superb results for most pens. Not recommended for hard rubber (Ebonite) pens."

My question is will readily available car wax help protect matte lacquer on my Pilot Knight
as well as Liquid Carnauba?
Or could car wax damage that coating?

3M paste wax, the best paste wax in the world, contains very little solvents, in fact liquid carnauba contains more solvents. Go ahead, knock yourself out with 3M car wax, for the price of a small container you'll get a whole can of 3M pastewax. 3M also sells one of the best hand rubbing compounds around, the "swirl remover" or something like that.