Also, if you are gonna do alot of hand stitching get yourself a stitching horse. A lot of difference having that to hold your work, well worth the cost and used they are only about $30 to $40. I machine stitch everything now and have for years. If you can go the machine route get one with a walking foot. Does a nicer job and you won't be rubbing feeding dog marks out of the bottom side of your sheaths.
I think what really sets good leather work apart from so so is several things:
1) Quality leather, you are just not gonna make a nice sheath out of a stretchy belly piece, don't care who tanned it.
2) Neat, even, tight stitching. If you are hand stitching practice, if you are machine stitching practice. You are looking for each stitch to be the same length and the stitching tension even. The threads should cross in the middle of the project not on the front or the back. If you back stitch two stiches at the beginning, back stitch two at the end, not three. Again everything should be even. Cut your threads with a fine tipped soldering iron. Carefully melt em so that loose ends don't show. In fact with care you can kind of meld the ends into the back stitch. Don't leave a burnt mark, there's that P word again practice. A stitching groover is an absolute must. Stitching must be inlaid to protect it and the groover will help ya get a straight stitch line too.
3) Finishing of edges. A lot of folks will get the first two going pretty good but then drop it here. Don't use an edgecoat product. Also don't dye the edge (unless the whole project is dyed). These shout out rookie move to an experienced leather worker and makes a guy look to see what you're hiding. The next step you've already got all the tools for. Using a 120 belt or a pretty worn 60 grit belt, sand smooth any edges that have been sewn together. Alot of times this is done before the stitching, just depends on the design of the sheath. As an example, you are working on a welted sheath edge. You have 3 layers of leather making up this seam, the front, the welt and the back. Use your grinder to sand these even and basically into one piece. No matter how good your gluing and trimming job, you aren't gonna get this edge even unless sanded. Sanding also helps remove any glue line visible in your welted edge. Hold the sheath pretty perpendicular to the belt to get things nice and even. Practice again cause you don't want to take too much off and make your stitch line look uneven. It needs to be an equal distance from the edge its whole length.
Get ya a good edger. In fact ya need a couple three in different sizes. These are really just knives and the same applies here regarding steel, heat treat etc as it does to a good knife. A $5 edger is gonna cut like a $5 edger. Keep your edgers sharp. The edge of a soft buffing wheel with some Jackson 51 works great. Your leather edges if done properly should be roundish not cut with a bunch of flat facets. If the edge does not have a stitch line like say the top of a sheath you should crease it. A creaser is one tool where the $5 one works about as well as a $50 one. Creasing provides a degree of finishing that is one of the differences between good work and so so. The devil is in the details. An edge that is just cut and not edged and stitched or creased just looks unfinshed.
Then rub your edges. I do it twice. Once, after wet molding and once again before applying the finish after the sheath has dried. Use a piece of canvas or a hardwood stick and literally rub it till it is slick, smooth and shiny. Ya can use yellow saddle soap, beeswax, or parrafin to help with step. Rub whatever you choose to use on your edge first then burnish it with your stick or canvas. Better yet get some Gum Traganath from a leather supplier. This will help hold the leather fibers down to produced a nice burnished edge. Finish with several coats of either Tan Kote or Bag Kote. Apply the finish with an old t shirt stretched tight over a couple of fingers. Apply the finish in the same direction on the edge. Putting this finish on your rubbed edges will help then last. If you have a lathe make a hardwood stick with several different sizes of grooves in it. Leave your stick spinning on high on the lathe. The lathe does all my edge rubbing anymore. It does it way quicker and better yet, even better than I can do it by hand.
Didn't mean to be so long winded. But follow these steps some and you'll knock your leather game up another notch or two.