I use just about any soap that doesn't strip off wax on my cars that get real dirty. Follow-up with Maguire's NXT Tech Wax, I also clay bar my cars at least once a year, its amazing how much crap comes off.
Now on my baby, I have never used the hose on her, she only goes out in nice weather, and I will dust first, remove any dead bug or grease, whatnot debris with Turtle Wax bug and tar remover, then use Maguire's quick detailer and a microfiber towel and wipe her down, then she gets a light rinse with a damp microfiber sponge, then Tech Wax, or if needed clay bar then Tech Wax.