Many people would argue it's not necessary to put grease over a round ball, so it's not an easy question to answer.
The "grease" thing has two reasons for existence: lube the bore to soften fouling and prevent chain fires. This can also be accomplished with a lubed felt wad under the ball. I don't use Buffalo Bullets, so I'm not familiar with their configuration, but I suspect the base of the bullet has a lubricant intended to ensure a seal against combustion gases leaking around the bullet and perhaps to accomplish the anti-fouling goal as well. In either case I imagine this obviates the "need" for an over-the-bullet grease application.