Wash and dry the potatoes and prick all over with a fork. Brush each potato with a light coating of vegetable or canola oil and sprinkle with salt. Place in the air fryer at 400°F for 45 minutes.
Let the potatoes cool in the air fryer for 5 minutes, then remove them and place them on a baking sheet or cutting board for easy preparation and clean up. With a sharp knife, cut each potato in half horizontally, creating two potato halves. Carefully scoop out the cooked potato from each half, placing it in a bowl suitable for mashing, leaving the potato skin boats intact.
To the warm cooked potatoes, add the butter, sour cream, half-and-half (or whipping cream), grated Parmesan cheese, salt, and pepper. Mash until smooth and creamy, and taste for seasoning.
Divide the mashed potato mixture between the eight potato shells. Top each with two tablespoons grated cheddar cheese, then sprinkle about a tablespoon (or more) of cooked bacon on top.
To serve immediately: Since you now have eight stuffed potato halves, place four halves in the air fryer at 400°F for 10 minutes to heat through and melt the cheese on top. If you want to serve the other four halves, remove the first four to a warm oven or cover them in foil, and repeat with the second batch. If desired, garnish with more sour cream and chopped green onions just before serving.