The easiest way to apply ice is to take an ice cube out of the refrigerator, hold it between your fingers, and then rub it on the nipple. Ice cubes are slippery little creatures and it can be tempting to wrap them in a tea towel or cloth to make them more manageable. Doing this will decrease how much the nipple gets chilled and diminishes the effect.
Instead of using an ice cube you can also use a freezer or cooler block. These are the blocks or bricks which you keep in the freezer and then pack in with your food and drink to keep them cold when you go on a long drive or picnic. These come in a range of sizes and the smaller, lunchbox-sized ones can be quickly slipped into a bra cup while the owner is wearing it. Be careful of these because they stay cold a lot longer than an ice cube and you shouldn’t leave them pressing against skin or nipples for too long.
Alternating between hot (flame) and cold (ice) increases the intensity of the feelings