There's no need to use Bore Butter with sabots since the barrel should be clean and dry.
The breech plug threads should be lubed with either breech plug grease, an anti-seize grease or even Bore Butter if nothing else is available so that it doesn't get stuck from the gas fouling that enters the threads.
The bore may need to be swabbed frequently to prevent loading difficulty, either between each shot or after every 2-3 shots.
Sometimes the 777 pellets can cause a hard crusty residue to form that can interfere with the sabot being properly seated on top of the powder when rammed. Be sure to note the depth of the loaded sabot by using the ramrod which can be marked for reference.
Make sure to clean the rifle thoroughly after each shooting session.
TC's T17 Solvent is formulated to make cleaning 777 powder residue easier, especially in the field.
Good luck and let us know how it shoots.
Here's a PDF of the Wildcat owner's manual: