Backed a yew bow for my Brother in law several years ago. As said above I used a dull scraper to get that waxy cortex off, then polished with 4-0 steel wool finished wih true oil. I think it was choke cherry and at the joints of backing, I skived the joints and wrapped with sinew for effect. Glued the bark down with TB-III. Wish I had taken pictures of it so I could show just how beautiful it came out.