I've heard several places that seizures can cause air-licking also. Plus, here's an article I found about some other causes:
Why Does My Dog Lick The Air? -
After the vet visit, if this keeps up, you could keep a video log of the air-licking, together with his paw-licking, and present the video log to the vet as a aid to him in helping diagnose his problem. I believe I might be keeping a journal of what you feed, when and your dog's scratching and paw-licking could also probably help your vet.