For the users of the app DiffusionBee at the time of this post, it currently does not support external flux models so I made a version to be able to use in DB. Its nase is SD 1.5 so you won't get the same quality images as a flux model but you can still create wood grain effects.
This model is based on wooden sculptures, still testing it out, but I have fun. Try using things like "Ebony wood" for darker grain, wood "sculpture", "wood carving" in your prompt.