The basket occasionally went in the dishwasher which cleaned the surface, but the well gunked grease has been building up.
Tried soaking the basket in soap and hot water. Scrubbing with a soft sponge. And then running the dishwasher multiple times but it only got a small part of the grease out.
Soak the basket in 50% vinegar: water. Then run the air fryer with some vinegar in it to clean out the rest of it.
Vinegar is an acid which works great on grease. Baking soda is basic and works great on carbon build ups.