The parchment sheet, just like the paper sheet, can be used on both faces, which are called recto and verso or even flower and flesh (hair side and flesh side) in order to better distinguish them: on the former, it is possible to catch a glimpse of the animal's hair follicles.
To further degrease the fur side (where the cavities of the animal's hair follicles are present) a dry technique can be used with stone or pumice powder (makes the surface less porous by closing the hair pores) or more superficially with pure ethyl alcohol at least 95°. Razor, sandpaper or pumice stone can be used to lower the thickness. The side that takes the glue best is the verso or carniccio.
To make it softer before gluing, you can wet it slightly until it loses strength and conforms to the surface.