A muddy car can be washed even in the shower, just take off the engine and electronics and blast it with water. But you have to take it apart after washing and clean + lube the bearings. Otherwise half of the bearings will rust up. Mainly outdrive bearings and wheel bearings often too. When you race in muddy or "sticky" conditions this is the easiest way. If you run in dry conditions then I don't use any liquid cleaning anymore. Its nice to see dark black plastics etc but it doesn't really do any good for the performance and that's what I'm after.
What I use for cleaning that takes out the oils and grease also is dissolved Fairy dish washing liquid. I disolve it in a spray bottle 1:10 and use it. Takes out the grease and washes off easily too.
We race here "club races" whole winter and championships in the summer. This winter the races were fortunately indoors but last year one small "club race" was like this. Guys who sell engines were very happy
It should have been last winter race on snow but you can see that the snow somehow magically turned into water
As it was seasons last race guys didn't care anymore and nothing to loose... except the engine and electronics etc.
Do not try this at your local track