Soap can easily hide out in seals, cracks, jams, lights, moldings, side mirrors and the grill area.
Pay close attention to the water when rinsing. If you see any suds or discoloration, keep rinsing.
Product residue can stain and cause a film to diminish your clarity and shine.
Always do a pre rinse with low pressure water, then presoak with a foam soap, hand wash, and thoroughly rinse to remove dirt, grime, and unwanted product residue.
Getting the water off your paint surface is equally as important as a proper wash. Both are about technique.