Buy a cheap toothbrush and take your bearings out of the car,
and get the dirt off your bearings. WD40 although it works well
for bearings is actually bad for them, they will build up dirt over
time and your left with a big mess.
I started using Team Checkpoint bearing treatment instead.
ONE DROP on each bearing is all you need. I witnessed a slight
increase in performance using that stuff.

I also used a damp wash rag to clean the chassis and such.
Make sure you remove your electronics out of your car before hand.
Water and electronics dont mix!