You can sight in just to get on paper and to get it close using some cheap Remington sluggers, and then fine tune it with the Buckhammers or other more expensive Sabot slugs.
You can use the sluggers which are rifled slugs, but they are soft lead and do tend to foul/lead the barrel which will effect accuracy unless you run a couple patches down the bore between shots.
My Tracker ll likes the Buckhammers, so I don't mind spending a little more since I'm using them for hunting with good results, and not target practice.