Used P21S for the first time with my Porter Cable. Product was effertless compared to Groits Best in Show liquid, which is what I've used as a carnuba topper. Went very quick and required only 2 pollishing bonnets vs. the 6+ that Groits would have required. I did however find the P21S to be quite hard. I really had to work at spreading the product on my pad with a picnic knife. I don't see doing 25 cars with a container. Seems more like 10-15. I'd appreciate everyones comments. Thanks. Mark