In a bowl large enough for the milk and chicken, stir together the buttermilk, salt, pepper and garlic until combined.
Add the chicken and let sit for 30 minutes. It can also be refrigerated up to 8 hours.
Stir in a separate bowl, stir together the remaining ingredients (flour through pepper).
Use a fork to pick up a piece of chicken, letting it drip off excess marinade, and put it in the flour mixture.
Dip that piece of chicken again in the marinade (with the other pieces of chicken still in there). I have the fork with chicken in one hand and a spoon in the other hand, with the chicken sitting on top of the spoon, to help the chicken not get lost in the marinade.
Drip off excess marinade and coat it again in the flour mixture.
Place in the prepared air fryer basket. The pieces should not be touching.
Once the basket is full, spray the chicken with olive oil.
Cook at 375 F (190C) for 7 minutes. Flip each piece over, spray with oil, and cook for another 7 minutes or until cooked through.
Cool leftovers and refrigerate in an airtight container for up to 4 days.