I switched from Blackfire Polyclay and lube to Zaino Z18 synthetic clay. For a lube, I use a capful of Zaino Z7 carwash to about 18 oz of water.
Zaino clay works much better than Blackfire. Cleans well, easy to mold and work, and the yellow color makes it easy to spot contaminents (i.e., time to fold the clay).
The Z7 car wash works very well as a lube. And it's very inexpensive; it works out to be about 30 cents per 18 oz. And, the best part is that it's just car wash. After claying a section with plenty of lube, I rinse with water, then after I've finished the car, I just rinse down with water and quickly go over the paint with a wet lambswool mitt (because I'm anal retentive) to make sure I haven't missed any soap residue.
Regarding standard, bottled lubes, one of the things that I don't like about regular lubes is that I have to re-wash the car completely and carefully to get rid of clay lube residue. That takes more time and effort. (In addition to the high cost of the lubes.)
Regards,
Dan.