Before burnishing the seams, they need to be made even. That can be done by trimming with a knife, some other cutting instrument, sanding by hand or with a Dremel, drill press-mounted drum sander or, as I did, with a spindle sander. It doesn't matter how you do it, as long as the job gets done. After that it helps to run an edger along both sides to make sure there aren't any sharp edges which don't burnish easily. That done, the seam got a quick wipe of dye to darken it and even out the color. The seams were burnished with gum trag and the chunk of fire hose I used before.
The next step was to wet mold the holster. As it worked out, the tip of the barrel is less than 1/4" from the toe plug on the inside. I love it when things work out.
The Sun will darken the holster some and give it a nice patina.