Yeah, I`d expect 8oz to last quite a while even if using a ton of product as per the KBM (which isn`t needed/desired with many abrasives anyhow and certainly not with Menzerna).
No idea on the Tire Shine as I go to the other extreme gloss-wise.
Leather care is a complicated topic on which few "experts" (scare-quotes not necessarily intentional, but watch out whom you listen to) really agree. I generally do fine with just an Interior QD used frequently, maybe doing a "full and proper job" every few years, but that`s just me. At the other end of the spectrum from IQDs are the Fat Liquoring processes and other multi-step approaches that can take many, many hours. In-between you have AIOs for Leather and standard two-stage processes with a cleaner followed by a conditioner and/or protectant.
Short version: I`d start with the two-step approach from Leather Masters or Sonus or Ultima or somesuch reputable vendor and then maintain it with an Interior QD.
Be careful to *not* use a cleaner that leaves the leather alkaline; leather is supposed to be slightly acidic.
Note that the conventional dogma of "today`s leather is coated and you can`t condition coated leather" has basically *never* proven true for me. But I do use a Protectant instead for the final step on leather interiors in great condition that I really care about. IME most "regular used car"-level leather will indeed benefit from conditioning whether it`s coated or not, but again that`s just me an YMMV can really apply when it comes to leather interiors.
