Add cut up quarters of raw potato and cook. The potatoes will absorb the excess salt.
sugar, ironically enough, neutralizes salt
quite easily.
Flat
Flushing with lots of water does help. You can spread gipsum (follow directions) and water that in also.
I don't know of any way to absorb the salt or counter act it, but you can always add more eggs and mayonaise to dilute the salt.