Circular or straight?
If you're working indoors, you can apply in a circular motion. The reason for this is because there's much less chance of errant dirt and dust getting onto the panels and creating swirl marks in the paint. If you're working outside, it's always a better idea to use up and down / back and forth motions, just in case any dirt or dust blows onto the surface while you're using the Paint Cleanse & Restore. Using this method, if any dirt or dust does end up on the paint, you will be able to tell straight away as the marks will be all going in one direction. Important to remember that Paint Cleanse & Restore is a non abrasive product, so it will not create swirl marks.
Work on one small area of the car at a time. I like breaking down large panels into quadrants. This minimises the chance of missing a section.
Apply using a gentle circular motion, making sure to go over the entire surface a section at a time. We like to do it with a pass over in one direction, say top to bottom, and then a second pass, still using the circular action, this time going from side to side on the same area. This is so you get the most effective cleaning done and don't miss any spots!