The BuckHorn is a good gun.
i'm not a fan of Powerbelts. IMO: The things cost too much.
Get some Hornady .430 or .452 240 grain XTP bullets and the sabots to go with them. If the sabots are too hard to load, try some Harvester crush rib sabots. Don't be concerned about melted plastic from the sabots; that almost never happens: i've never seen it.
Hot soapy water does a good job of cleaning the bore and breech plug. After cleaning with hot soapy water rinse the bore with hot water folllowed by two or three dry patches. After cleaning, lube the bore with a good gun oil. Be sure to remove all traces of oil from the bore with a patch moistened with alcohol before loading the gun: This often prevents a hard ring of crud from forming in the rear of the bore. This "crud ring" makes loading difficult.
Lube the threads on the breech plug with anti-seize before installing it.
Good luck with your muzzleloader.