I only have 4 model guns. I have used the customers for just about all of my builds. I use plastic wrap to wet mold then as JLS says, I wipe it down very well. The customer knows this is how I do it, so no surprises and I think they like the fact that I fit the holster to THE VERY GUN it's being made for. As for leaving the gun with me? I have a safe I keep them in, and the customer comes to my house to drop it off so he knows where it is. I dont do this as a business per se but as a busy hobby. If someone really wants me to build a rig but lives far away, I'll up my price a little and order the blue gun (my fav) if one is available. The customers are surprisingly fine with this. I'm pretty sure I have jls' pdfs on holster design if you need them, send me a message. They worked great for me and is the method I use.