You folks know best ;D
Lemme guess the dilemma you have with shell - they were not coated with bullshit finishes like the ones from Alden, and as a result, they suffer catastrophic rain and water problem. Am I even closed to be correct? Because as far as I know, you have some St. Crispin shells, and per my knowledge, St. Crispin only polish their shells and not coating them with anything.
part of teh reason behind all this confusion is that (a) cordovan is finished slightly differently by each maker, (b) different cordovan batches welt/shine differently, and finally, (c) you can put a wide range of products on them without ruining them, so everyone counts their success in making them look good as evidence that theirs is the only right way
Give it a shot at the basic products first, then move on to experimental stage(s) later on. AFAIK, Glen Karen cream works perfect with shell, even though Glen himself never proposed the cream for used with shell. Pat had great results with Glen Karen cream, and so was myself.