At least i don't know if there exists a tutorial.
In the ModDev/Locations folder, go to the joesville/JoesVille_Speedway folder and open the JoesVille_Speedway.scn file with a text editor.
Scroll to the end of the file and you will find 3 sections.
ReflectionMapper=REFLECTEDENV
ReflectionMapper=STATIC01
ReflectionMapper=REFMAP0
where all the instances are listed, that shall reflect on the car and on the (wet) track.
The last section should be the one for the cars, because if i use the reflection mapper for a car, i have to add REFMAP0 to the material settings.
You can test it, if you enter that section (if they are not there already) into a scn file of a track where it happens and see if that solves the problem.
Use the JoesVille_Speedway.scn file as the example how it has to look like.