One thing also you can do is I glue one side of sheath and matching welt, when it is almost dry I align them together. I then use a small square faced hammer and hammer with over lapping blows. I then glue other side of sheath and welt then when ready apply them together. I hammer again back...
I start with a 50 grit then 120 then 400 grit pre heat treat on 154cm. AEB-L post heat treat I do 50,120, Trizact A65 then A45 and hand sand. Damascus I do A 30 pre etch. On 154cm after heat treat I do 120, trizact progression again.
I sand with an 80 grit belt then use an edger for the corners. I dampen the leather then rub with saddle soap to smooth , next a hard plastic piece to rub to smooth.