That's a nice first holster!!! you should be proud of that. All I use is NFO and a good outdoor type waterproofing and sealer for leather products, Fiebings golden mink oil, with nothing applied inside to attract dust or dirt, use the best leather, and you don't need it. Apply the nfo first to the outside, then the waterproofing sealer. It gives a very natural hand rubbed finish. An unlined holster is just as correct as a lined holster, probably more so in a slim jim, as they are a period type piece usually for black powder.