TexasCHLforum.com

The problem with Mink oil (or any leather oil for that matter) is that it can soften the leather too much and degrade the holster's retention capability. Most holster manufacturers I know of recommend against oiling their holsters.

For some holsters, this must be done while wearing the holster. This is because some holsters' geometry is changed by threading a belt through the slots/loops/whatever and cinching it down, making the holster fit the gun tighter.