RCColt
what you've got is just plain wearing where the holster comes in contact with the trousers. If this holster is only 2-4 weeks old, this should not be happening this soon. Is your customer complaining about black on his/ her trousers?
The process that I use is, [for black only] dye black , lightly oil [if no tooling I rub the oil in well] , I use acrylic resolene product from Feibings as my finish coat. I submerse my holster in 60 resolene 40 water. I completely saturate my holster in this mix, pull it out and wipe it down and let it dry. You'll might notice that black bleeding into the mix. that's OK Let your holster air dry and cure out for 24-48 hrs. I have high humidity down here so I prefer the 48 hrs.
I prefer not to dye my anything that I make with black ! the color just doesn't seem to last and there is a higher probability that it will off onto someones clothes.
I hope this works.. I've used this process for 8 years while I was making black duty gear for the local pd
Happy tooling
Tim