Steve -
I didn't have to finish the blank on the bamboo rod that I built last winter, but on the wraps I used Ace Hardware Brand Spar Varnish based on the recommendations of a good number of rod builders on a couple different websites devoted to bamboo rods, thinned about 25% with Sunnyside Brand pure gum spirits turpentine. Sunnyside was available at the local Ace Hardware store.
I am quite pleased with the finish on the wraps. Seems likely you would get the same quality of finish on the blank.
John