Hackberry is in the elm family, you shouldn't need to chase growth rings ( unless it has really small rings and you have to get down to some bigger ones below). just remove the bark and the cambium layer. Below that is your bow back. make sure to heat treat for added durability and performance. IF your going to chase, i heard some people use stain and such to wipe on real fast so you can see the grain and layer pattern. Just what i hear, i've never used that technique myself.