If you really want flaky you want NOT to foil prior to cooking your potatoes. Foiling prior to cooking locks the moisture in and 'steams' the spud. Cooking bare will crisp the skin AND allow the natural moisture to escape during cooking. This results in a much nicer baked spud, IMHO. If the occasion allows, I wrap the spuds in foil sheets upon removal from the oven/cooker.
The alternative is to foil with a good coating of rock or kosher salt prior to wrapping. This allows the salt to absorb some of the moisture. Even then, I prick the foil a bit to allow the steam to escape during the cooking process.
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