A suction cup? No way unless maybe you are talking about a big dent. The process is pretty fascinating to watch. They set up a grid like device that projects on to the dent. The dent makes the grid look out of focus. They use several tools that look like riding crops and the literally massage the dent out. When the dent is out the grid looks clear. he also used a plastic mallet to tap something that looked like a nail finisher/tap that is also made of plastic. he tapped around the dent very lightly with that gizmo. I watched my dent guy do a long dent in the door of my wife's car. Took him an hour but it perfect when he finished. I've never seen them use any suction cup devices. I believe there is a kit available on line with an instruction course. The kit is expensive.