I have a small set of needle nose pliers. After I drill the main hole I insert the meddle nose pliers and rotate them in the hole and this makes a perfect countersunk hole of compressed balsa. Works for me and never had one fail or pull out. Also I use gorilla glue to glue them in. Just rub a little oil on the coating around the hole, not in the hole of course, and the foam from the glue will just easily break off after curing.