My '06 has mild amounts of orange staining starting to occur in various places on the underside .... mostly frame and body bracketing. On the waxy stuff ....... never noticed it but I probably just wasn't paying attention .......
The waxy stuff is about the best - there's a local shop here that does it and is very thorough ..... you have to leave your vehicle for a number of days, they clean it and then pull
all interior panels (no drilling) and coat everything. Takes 'em between 3 and 5 days to do the whole enchilada, IIRC. They recommend a touch up once per year after you have it done.
My wife's 2000 VW Passat came with waxy stuff from the factory ...... best factory rust protection I have ever seen, bar none. Would buy another VW in a heartbeat. (My bud's 80's Vanagon went for around 600K+ and was still looking pretty good when he got rid of it)
Next best after the waxy stuff is to have it oil-sprayed ..... it's more of a temporary solution ..... you should have it done at least once per year (probably twice, spring and fall) cause the oil will wash off to some extent (unless you drive on dusty roads alot
) Some places used to do this with used motor oil ...... probably not the best thing environmentally speaking, I'd guess most are now using something a little more green.