I like a plastic finish too. But much of my bowmaking is done in the depths of winter in an unheated garage. I use Watco danish oil or teak oil in the same manner as Roy describes for tung oil.
It is a pretty finish, smells great and can be applied anywhere, anytime. When conditions allowed and intended use warranted, I have applied poly over oil finishes on bows. Particularly for ones I have made for week long backpack hunts out west.
I have no problem using oil finished bows in the worst of weather for day hunts back home. You can apply subsequent coats to freshen up the finish whenever you like.