Casting only pays if for itself if you intend to shoot allot. Otherwise the simple procedure of buying your projectiles is a better and much cheaper way to go if you consider yourself just an occasional shooter. I've always figured if ones ball and patch combo are 0.005 overbore your are at the optimum in engraving its projectile in most P.RB barrels. As a 50 cal bore size patch and ball combo (.490 & .010) usually gives mediocre result's at best. .490 & .015 or .495 & .010 are about as good as one can expect for accuracy. .490 & .020 or .495 & .018 will exhibit nothing better than a strenuous reloading exercise for its shooter.
As far as making ones own patch lube. About the only benefit is the removal of unwanted scents like wintergreen and some other nasty smells over what is made commercially. The use of Ballistol and diluted with water is indeed a good patch lube but still has a odor to it not found in Nature. And there lies the problem Sir. So many hunters spend so much money and time in their trying to be Sent-Free whenever they enter Mother Natures domain. But have forgotten, don't bother, or even consider the scent of their items brought into the field /woods with them. (gun, its bore chemicals & lubes, accoutrement bag, gloves) Simple forgotten or ignored things that can unknowingly ruin a hunt.
I prefer Wonder Lube at my favorite gun Range for a patch lube. Or Ballistol and water mix in a pinch. But for a patch lube in the field I have a recipe that contains a few different ingredients. Two of which are Lard and Lanolin in its make up and has little or no scent. So if you intend to make your own patch lube. Try to make one that doesn't smell any worse than the environment its to be used in. Just my opinion is all. What works for me may or may not work for someone else or collide with their way of thinking. That's to be expected no doubt. Good Luck OP.