A variable suction can feel fantastic and it can be increased to hellish pain.

A simple jar (Peanut jar or spaghetti sauce jar) with a small tube (aquarium tubing) can be placed in the jar and then pressed to some lubed balls. The suction pulls them in and makes a seal despite the tubing. Hairless is best. The more suction the more pressure it places. Careful not to make em pop. Use caution.