In the case of the air fryer, I hold the basket over the sink and spray a fine mist of olive oil on the surface of the basket, lay the french fries in there (crinkle cut are my favorite because there is more 'outside surface area' exposed) then spray a fine mist on the french fries, sprinkle them with salt (I like sea salt) and put them in the "pot" of the air fryer to begin heating.

Much experimentation here!