If you'd like to ease into to breast impact play, perhaps with a curious partner, try bamboo skewers, available in the cookware section of every grocery store.
Simply beat the breasts, labia, inside of thighs, etc., gently, with a bamboo skewer or, for more "pizaaz", bend the skewer and then let it go, allowing the tip to strike a sensitive part of the body.
No intense pain and no dramatic bruising or trauma as might be caused by using a paddle, cane or length of hose.
As a bonus, using the sharpened end to drag over sensitive body parts (nipples, labia, prepuce, vaginal introitus, inside of thighs, stomach, etc.) is a great way to build up anticipation, dread and sensitivity.