Preheat oven to 400°F
Scrub and dry russet potatoes
Pierce each potato several times with a fork
Rub potatoes with oil and salt
Bake potatoes directly on the oven rack for 45 to 60 minutes, until tender
Remove potatoes from oven and let cool slightly
Cut each potato in half lengthwise
Scoop out the potato flesh into a bowl, leaving a thin shell
Mash the potato flesh with butter, sour cream, milk, salt, and pepper
Stir in shredded cheese, cooked bacon, chives, or other desired mix-ins
Spoon or pipe the filling back into the potato shells
Top with more cheese if desired
Bake again at 375°F for 15 to 20 minutes, until heated through and lightly browned
Garnish with chives, bacon, or sour cream if desired