i have never shipped corals before but I heard that thermos trading with frags
basically you put the frag
to be traded in a bag filled with tank water. Place bag inside thermos and ship. The person you are trading with does the samething. I think you keep the thermos after the trade to be used again for the next thermos trade.
Or you can ship the corals in a bag of water placed inside a styrofoam box with a heat pack (depending on the weather)
People usually ship next day or overnight or something.