You want to wash your car first dry or leave a little water on the car is fine.
Next break the bar into two pieces then use one bar and fold over itself on top so a clen side is exposed always and use the Clay lube supplied by the clay manufacturer it is better than using soap water as a lube.
After each section wipe e residue up and move on to next section to clay start at top and do the bottom sections last.
If caly gets too dirty use second batch of clay that you broke off.
Use plenty of lube to clay and if you drop the clay throw it away do not use it !!!
If car is new or like new then that slhild be good enough but if it is older then you need to use a cleaner like Megiuars Deep Crystal cleaner.
Good luck
