I'd first advise you get a bore light which will drop to the breech plug and take a good hard look at the bore. Most secondhand muzzleloaders I have seen have had rust pitted bores and/or rings from firing with a ball not fully seated and that rifle has been kicking around for 30 years or more. As a general rule I will not buy a used ML rifle unless I get it cheap enough to afford to replace the barrel. On the buff hunter that would be pretty much out of the question.
You will want a steel ramrod for the buff-hunter, the thimbles only take a 5/16" rod and in wood that is way too flimsy for a .58 caliber, which is probably why it has no ramrod. The Zouave rod is only about 1/4" diameter, will rattle badly in the thimbles and is hard to hold on to if you need to ram a tight load or worse, to pull a load. I'd go to the hardware store and get a 3' length of 5/16" steel and a brass pipe fitting which can be slipped onto the end of the rod, soldered or JB Welded in place and filed or ground to a nice contour to fit the bore.
The twist is listed differently from different sources but it is a slow twist, somewhere around 66-72". The Buffalo Hunter is not "rendezvous legal", being post 1840, and not legal for civil war events either, being not military issue. That leaves hunting, and for that I would highly recommend the patched round ball. While it is true that a well placed minie will drop anything on the continent, the low velocity and rainbow trajectory makes shot placement a bit difficult, not to mention it will kick like a mule in that little rifle. The load recommended by "filmokentucky" will leave the muzzle at only about 900 fps. Zeroed at 50 yards it will be 4" low at 75 and 12" low at 100. The round ball will shoot much flatter, kick less, cost less and be easier to find an accurate load, while still being more than enough for any game out to 100 yards. My Zouave is reserved for elk hunting with round balls only, I'd prefer the lighter buff-hunter but they never were common and are downright scarce today. If the bore is good, you have a real find!