Llube on a patch does (PRB loads)make the ball/patch combo slide down the bore easier. Patches of any kind, greased or not, are NOT GASKETS -in fact, they have the opposite effect. TheyDO NOT increase the seal between the bore and the ball.

Unless a ball obturates completely, filling the grooves to the bottom, there will be some gas that blows past the ball. The thicker the patch, the more pronounced this effect is. So don't expect a greased patch to give higher velocity.

However, anything that allows you to slide the ball down easierwith less force on the ramrod helps keep the ball in as pristine a condition as possible, and also lets you seat it on the powder uniformly each time,contributing to accuracy.