With that being a whitewood (is it ash, or hickory or something else?) you're going to want to get it properly sealed against moisture or you'll end up with it following the string like crazy. Whitewoods are terrible when it comes to sucking up moisture and it really affects their performance. On the yew bows I make I always go for Danish Oil (beeswax, linseed oil and turps) followed by pure beeswax rubbed in, which is a fairly trad approach and works well enough on yew to protect the bow against sensible levels of moisture.
On ash/hickory bows however you're going to want a proper, decent varnish or sealant otherwise you'll end up with a banana eventually. Personally I'd avoid fully "traditional" finishes if you want it to perform well, and go for a quality yacht varnish. You could of course then put a few layers of pure beeswax over it and gently polish until you get a nice, low-lustre finish which will look like a traditional finish but with the added protection you will need with these types of wood.
Failing that, if keeping it totally trad is more important than keeping it snappy, go with boiled linseed oil, refined Danish Oil or simply lots and lots of coats of beeswax!
