Slice the pickles into ¼-½" slices and toss in all purpose flour to coat.
In a shallow bowl or coating tray, combine beer or water with egg and mustard. Whisk together. Sift in the flour a few tablespoons at a time and fold the flour into the wet batter after each addition of flour. You don't want to whisk it in or you might develop too much gluten and it will become gummy. Only use enough flour to get the consistency of the wet batter to that of a thick pancake batter.
In another shallow bowl, mix the breadcrumbs with the seasonings.
Dip each pickle slice into the wet batter and then into the breadcrumbs. Set the slices on a cooling rack or parchment lined tray.
Preheat the air fryer with the basket or cooking surface inside on the hottest setting for a full 10 minutes. Spritz the basket or cooking surface with a neutral flavored oil. Lay the pickle slices in a single layer. Air Fry for 5 minutes or until they are golden brown. Remove the pickle slices and cool on a cooling rack. Repeat if you have multiple batches to air fry.