Howdy
I read about using toilet rings years ago. Never used them myself.
Back when I started shooting Cap & Ball revolvers in 1968, the standard was to gob some Crisco over the ball in the mouth of each chamber. I found this was less than ideal because while shooting during the summer months, the heat of a round going off in the chamber at battery would melt the Crisco in the next chamber, the next one to be fired, and the melted Crisco would mostly run out of the chamber.
YES, covering a ball with lube absolutely will help prevent a chain fire. In the event that there is a small crease or other deformation in a ball, when it is seated the ring of lead shaved off may not be a complete ring. There may inadvertently be a void in the seal between chamber and ball, allowing a path for a loose spark from a round being fired to find its way to the powder charge in another chamber. Back in those days I had a chain fire with my old 44 caliber brass framed 'Navy' and I never did figure out exactly why it happened. I always suspected the melted Crisco may have run out of a chamber and allowed a spark to find its way past an imperfection in the seal of ball to chamber.
Many years later, I discovered lubed felt wads. They were marketed as Wonder Wads and as far as I know they are still available. I would position a Wonder Wad between the powder and the ball. No, the lube did not adulterate the powder. A 1/16" or so felt wad between powder and ball made a much better spark arrestor in case of a poor seal to the chamber, than a thin ring of lead.
You don't really need a lot of lube in a C&B revolver. The lubed wads are fine. And they help scrape out fouling left behind in the bore from the last shot.
Yes, lube for Black Powder cartridges and lube for a C&B revolver are different. Years ago I used to make up my own lube for bullets from a 50/50 mix of beeswax and Crisco. I pan lubed all my bullets with this stuff.
Years later I switched to SPG sticks in my Star Lube Sizer for the Big Lube bullets I used to cast.