Tip: If you are using russet potatoes, never overbeat them. Russet potatoes will give you the fluffiest potatoes but they’re also the easiest to mess up!
1) Use a hand mixer. The primary reason for rubbery mashed potatoes is overworking them. Over-beating breaks down the cells and releases their starch, resulting in paste. Only mix the potatoes for a couple of minutes – when you are using REAL POTATOES, they should still have a few lumps in them, they’re not supposed to be as “smooth” as instant potatoes!
3) Avoid food processors. It may seem easier — especially if you’re trying to cook multiple dishes in the preparation of Thanksgiving dinner — but food processors are just too harsh on potatoes and will never give you the fluffiness you’re looking for. Take the time to mash them by hand or for a short period of time with a hand mixer!
3) When in doubt, do it by hand! Use a hand held potato masher or ricer to mash the potatoes right in the pot (or crockpot). The risk of overworking the potatoes is much less likely with one of these devices.