Atoms have either a positive (more protons), negative (more electrons), or neutral (equal # of protons and electrons).
How conductive materials are depends on their atoms' ability to either give-up or gain electrons. Enough of that.
Due to the molecular make-up of "plastic" materials, they are considered to be purely non-conductive. Therefore it is very easy to disrupt or change this molecular make-up with the slightest amount of friction, heat or pressure and cause it to obtain a charge...
static electricity. The plastic on your motorhome becomes "charged", if you will, while traversing up and down the highway and attracts the 'neutral' dust/dirt particles.
If you can control this conductivity, you can theoretically control the static electricity. Moisture and anti-static sprays/liquids are a few ways to accomplish this feat.. Keeping the plastic on your motorhome 'wet' continuously is not feasible, as I see it. An anti-static spray/liquid may provide what your looking for.
Even though the detail type sprays you mention will work briefly, (until they dry/flash-off), you'll probably require a more dedicated anti-static spray/liquid. The anti-static sprays/liquids are usually made so that when they've dried/flashed (solvent carrier) they leave a protective coating that will be difficult to generate static-electricity through.
Here is one anti-static spray/liquid:
3M? Sprays
If you go to your local electronics/electrical supply houses they have others. Asking their advice may also be of assistance.
Without delving further into "The Sciences", in some way, I hope this helps.
Bob