Guys - this is a video of my brother loading the Virginia rifle he built - 44" bl. .50 cal. 'Rice' barrel. He's using a .495" ball and a .022" denim patch, lubricated with windshield washer fluid, the -45 stuff, mixed with a couple ounces of liquid soap. We've stopped using soap now and use a couple ounces of Neetsfoot oil in about a litre of fluid. A litre is 33.8oz. compared to the US quart of 32oz. The exact ratio is not important. The oil is just to slow the evapouration of the patch lube. For hunting, we use staright neetsfoot oil or mink oil from Track. He is using a range rod so he doesnt' have to keep taking out the rifle's rod and replacing it. We load pretty much the same with a range rod as we do with the rifle's rod.
We've been shooting BP rifles and smoothbores since 1970 for him and 1972 for me.(aside from the left handed flintlock pistol he build at age 16 - all parts hand made including drilling the barrel.

I should also note at the time he loaded this, we'd been shooting for about 2 hours, maybe 25 or more shots each - no wiping at any time. With a good thick patch and descent sized ball, the fouling present in the barrel is only from one shot, the previous one. As you load, you are wiping the last shot. If fouling is building in the grooves, something is wrong with your combination - the ball size, patch thickness, crown or maybe even the lube which is of least importance. The crown is the most important aspect of the load as it needs to be right, or it will not allow you to load a tight enough combination.