Dirt Sprints are normally run on the longer outside (Short Circuit) track, in the clockwise direction. Timing is as per most othe sprint events or hillclimbs where only your fastest time counts. Typically each run is two laps, as per Autocross with 6 runs, but can also be run as three laps over 5 runs. The witches hats still line the track, and penalties are the same as for the Autocross events. Crossing the imaginary line is a 5 second penalty. Dirt Sprints can also be run using a combination of tracks, and timing can be a little different.  It pays to check the supplementary regulations for exactly what type of event and tracks are being used. The same basic rules apply to Dirt Sprints as Autocross. If you have a vehicle that you have run in Autocross, the same vehicle will be OK in Dirt Sprints.