I use alcohol exclusively. It dries in just a short time and the gun doesn't need plastic on it. I make the holster and leave the edges past the seams rough because they trim so much easier when the leather is saturated with alcohol. I have an old round tin cake box which I put the holster in and pour the alcohol over it in there. When the front side of the holster is well saturated, put the gun in it and then use something smooth and blunt to press the wet leather into the shape of the gun. I use an old piece of polished deer antler but almost anything, including knuckles, will work. The gun stays in until the leather is mostly dry. You can tell when it has dried enough because the leather, though still feeling wet, won't form to contours any longer. Of course, you can leave the gun overnight and that will surely do, but much shorter time, maybe 45 minutes, will usually be enough. I always mold a crease in the holster for those tall front sights so it doesn't cut through when the gun is holstered and unholstered and that crease is the place dryness can be tested by pinching. After working the wet leather, you can tell by the feel of that crease when it won't work any longer.
Steve