I purchased a DeSantis holster for a Colt Mustang and it is very tight. I have worked the edges of the holster with my hand to soften it up. The gun does fit in the holster better, but it is still very tough to get in and out. Is there any type of oil or "grease" or something that can be applied to the inside of a holster to help break it in? If not, is there something I should be doing that I am not?