Never worked with Horse hide but I can say that if I want the thread to stay looking the same I simply glue up my holsters, sheaths,etc with contact cement. After I have completely finished dying, I then sew up the sheath or holster. After dying I have a crock pot with hot bee's wax/mink oil/neats foot oil mixture that I dip the item into. Once the item has soaked for about 30 seconds I put it into a toaster over on warm for about a minute. I then buff with a very soft buffing wheel, one I use strictly for buffing leather. This process waterproofs the item inside and out and gives a nice satin finish. The heat from the oven hardens the leather giving me a rigid holster or sheath.