I sealed my ash arrows with 3 rivers dipping lacquer. As mentioned above tongue oil works well, I have used it on some cedars I made up and it does add quite a bit of weight. If you use the oil to seal the shafts to get the fletching glue to adhere well and/or you want to do a cresting you will need to let the shafts set out, preferably hung up, to completely dry so you can’t feel any oil on your fingers while handling them.

Troy