Wash the potatoes and pierce each one with a pairing knife. Place the potatoes in a single layer on a large, microwave-safe plate.
Cover the potatoes with a wet paper towel. Heat on high for 5 minutes. Flip the potatoes. Microwave the potatoes again, for 5 - 7 minutes, or until they are tender.
Place the potatoes in the refrigerator for about 20 minutes to cool. Slice the potatoes in half. Scoop out the insides, reserving the cooked potato for mashed potatoes later. Leave about a 1/4-inch border of potato inside in the skins.
Brush the insides of the potato skins with the reserved bacon fat.
Place six of the skins inside the air fryer basket - skin side down.
Cook for about 10 minutes at 400 degrees F. Open the basket and fill the insides of the skins with the shredded cheddar cheese. Heat again at 400 degrees for 3 - 4 minutes, until the cheese is melted and bubbly. Repeat the process with the remaining potato skins.
Top the cooked potato skins with the cooked bacon, scallions and sour cream to serve. Add salt if needed.