I do use gum trag to finish the inside on all of my western holsters, unless they want them lined. I can turn the holster upside down and shake them, the gun will not fall out. I have never used it on a pancake, or CC holster though. It's a slicker finish but not so slick that the gun will just drop out. I won't use anything else on the inside. I just like the way it works. When you mold a holster properly, I do not think the inside finish has much to do with the gun falling out. Just my opinion. I hope it helps a little.
Frank