I have never read anything about using salt to help ease the fish's discomfort after an ammonia spike. It could be possible, but I haven't read anything. I was wondering if you meant "nitrite spike", since aquarium salt does help with that.
I bought a betta once with already inflamed gills from a high ammonia level. I used Maracyn 1 or 2 on him, and it seemed to lessen the redness and swelling, but the rust-colored marks on his gills remained the rest of his life. But I don't think you would allow your ammonia to be that high for that long.

Just keep monitoring your ammonia level to make sure you're past the mini ammonia spike - I know you will!