“...3-in-1, Kroil, et al. are penetrating oils...”
What do you think of 3-in-1 for general use on firearms? ... bike chains, O-ring chains, and in situations where the oil may contact finished wood or plastics?
I’m not sure what I’d use it for, other than removing rust. In general, I don’t use it on firearms, so cannot comment on its suitability. I use it to free rusted bolts on machinery. I clean it off, and use a heavier oil or grease when reassembling. I have never seen 3-in-1 or Kroil damage finishes.
Note that I’m not claiming to be an expert on gun cleaning ... I merely mention a few things that I find useful.