barrel care and shooting load
To prevent surface rust, thoroughly clean and dry the bore after each session, then wipe the exterior metal down with a rust-preventative oil like Barricade, Ballistol, or a light gun oil. If it's just a patina finish and in light surface rust is already present, very fine 0000 steel wool or Scotch-Brite with oil will usually remove it without harming the finish.
For a .54 caliber Woodsrunner, most shooters get good results with 2F black powder. We recommend a .535 round ball with an .018" patch and around 60-70 grains of powder. Note that Woodsrunner barrels are designed for patched round balls rather than conical rounds.