Pardon my naming of items, cannot recall the exact names of them.
I like to use a little gouge to cut out the line of the stitching. Works best on veg tanned leather. It's adjustable as to where the line is cut out in relation to the edge of the leather.
Then there is a device with a wheel that looks quite like a pair of spurs. You run that along the line you cut with the adjustable gouge with a bit of downward pressure. That gives you evenly spaced stitch marks.
You will want some sort of thimble to ease the pressure of the needle against your finger.
A pair of pliers helps somewhat in pulling the needle through the leather, especially if you have three or four layers of leather to go through.
I also like to use Barge Cement to glue pieces together before stitching. That really helps.
I also used to use a belt sander with about 40 or 60 grit paper on it to even out the edges. Then there is a tool called??? that will trim the edges after you sand them. Then a burnisher (looks like a small wooden pulley. Spin that on a drill press or a lathe and lube it with beeswax and that gives a very nice finished appearance. I have even taken a 3" long piece of dowel and cut a groove in it with a rat tail file. That works just as well.
All I can think of right off hand. All that stuff should be available from Leather Factory or Tandy or
?
Have fun,
John (Bigsmoke)