look for consistancy across each panel as a whole, if he presses too hard there will be holagraming which will flicker in the sun light as you walk round the car,
so yes in a nut shell you will be able to see if he fooks up anywhere, also be awair that when hes been over the car with the machine it may uncover things you couldnt see before.
can anyone else elaborate on what ive said as im no good with words really, better explaining it when its infront of me;)