Don't move off until the Reloaded message comes up.
The rearm Pads are sometimes just off the runway on the perimeter track, sometimes at the side of the runway, but once you see one you will soon pick them out easily.
Although shutting down the engine maybe a good idea to help cool off an engine that is hot through use of WEP, you don't have to. The rearm will happen as long as the aircraft is stationary. Move a bit before its finished and the 30 seconds will restart again.