Good tip which I always do is head straight to the laserwash after the skidpan as it gets 80% of diesel off including underneath the car. Bloody good job for $10 I then go home and give it another once over and paint is all sweet.
Laserwashes that I know of relatvely close by are at Beenleigh or Acacia Ridge (Shell Servo Granard Rd)
Cheers,
Shane