Unless a band saw blade is so bad that it cuts hard to one side or the other, you can cut straight with it as long as you don't try to use a fence. Just mark the line with a soft pencil and angle the work piece so the saw cuts where you want it.
If the blade wanders back and forth sideways, then you need to adjust the guides. Cheapest saw there is can me made to cut where you want it to on freehand work.
Sharp blades are key.
I made several bows entirely with hand tools when I started in the late '90s. Would never do that again if my purpose in making a bow was to shoot it. If your purpose is to gain or hone primitive skills (as is probably true of the majority of us on this forum) then hand tools it is. Hatchet to get close, draw knife, spoke shave and scrapers after that. It's all rewarding.
Jim Davis--Reparrow man