strop refurb advice

I recently bought a very neat little razor box with a strop on top of it. The strop was very dry, but I, ever the optimist, am trying to make it useable again. I cleaned it with dawn dish soap and a nylon brush, then gave it a little mineral oil to bring back the pliability. Well turns out the little strop is really in nice shape under all that old crud. Problem is, I can't seem to get rid of all the old crud. I worry for health and hygiene reasons mostly. Anybody have any ideas how to get the rest of that stuff out of it? It's blackish and greasy. I suspect it might be old strop dressing, but really don't have a clue. It could be thuringian slurry as well, since that's the final feature of the neat little razor box. :) Oh, the strop is nubuck material btw. I see ads for nubuck degreaser..Anybody have experience in it's use? Or just any ideas on how to make it safe to use directly pre-shave, without having to disinfect my razor each time? While I'm at it, what's the purpose of strop dressing anyways?

Get some Goop handcleaner, the stuff mechanics use. I would suggest some neatsfoot oil as well and apply this after the last cleaning and the leather has had a chance to air dry.

Will Fast Orange work the same?