When I first received my Rockie in Mercury, I immediately sprayed Danier Leather Defense spray (after patch testing, of course). I did two layers, just to be safe. I don't wear jeans too often so I haven't experienced any possible denim transfer, but in terms of dirt and other colour transfer, so far so good!
Oooh!!! I never even thought of Danier. Do they have a leather cleaner as well?