There are several methods to add lining to your leather. My favorite lining is full grain cow/calf leather but others use any one of several leather products. I personally think deer would be a bit fragile for the job but do know it has been used before. I have used at least three good glues for this job, check with your local Tandy store for personal help and a good glue, properly applied, will keep the edges together. There are several ways to apply the lining but I think most would agree that something like deerskin or even suede does not need to be rolled in. I do most all of my glue work on liners flat but some prefer rolling the liner in for a smoother finish to the fold. There are several good videos out that really show several methods of doing this along with a lot of other holster making ideas. Just an added thought, you probably realise that the liner has to be sewn in after the glueing has dried?