Be cautious when using "slipperier" lubes. I did a study where I compared spit as my lube with a commercial lube that was reported to be quite slick. I fired several rounds of each lube over a chronograph and found that with the lube that was "slipperier", my standard deviation of my muzzle velocities was significantly greater. To me, this means that when a lube is too slick, it allows the bullet or patched ball to start moving sooner. By moving sooner, it results in varying breach pressures and resultant greater variations in muzzle velocity. These variations in muzzle velocity cause a loss of accuracy. So, use caution when selecting lubricants and try to avoid those that may be too slick.
If you read Dutch Schoultz' "Black Powder Rifle Accuracy", you will find that he, too, addresses the issue of lube slickness and that some lubes can be too slick. He first addresses it on the first page of his segment entitled "A Consistent 'Dry' Patch Lubricating System"