you are doing it correctly. you want to continue to stay in an area until it feels smooth. if the clay is starting to leave remnents or streaks add more of the lubricant to the area. dont move to the next area until the surface feels smooth. If you listen as you claybar, you will hear as it removes impurties. once all the impurities, ie oxidation are gone you will no longer hear anything and the surface will be very smooth, so move on.
Work in small areas so you dont miss any spots. a 2x2 section sounds about right. if you have a dark truck, ie black like mine, dont use a circular pattern this will leave swirls in the clear coat. i use a back and forth motion instead of circles.
Also make sure you continue to kneed the clay ocationally. Also if the clay hits the ground through it out and get a new one. when i take a brake i put the bar on my windshield resting on the plastic because i feel it is a clean and there are few impurities there. also it wont leave a mark there either.
AND very improtantly make sure after you clay bar you wax the truck. when clay baring you are taking off the wax and a small part of the clear coat so you need to wax it to add back a protective layer. i think of it like shaving. after i shave i use aftershave to protect. just think of the clay bar as shaving and the wax as the aftershave. if anyone has a better analogy please let me know.