Re: Midwest FJ's.... Rust!
do like Mike and cover everything down there with fluid film (or Boeshield, same stuff, different mfr.)
if you already have surface rust, convert it first with some sprayed on Ospho (phosphate), to turn red iron oxide into black, inert iron phosphate, then cover that with fluid film
Use a cheap garden sprayer for the Ospho, and protect your face/arms (it will sting), and then use the simple compressed air sprayer Fluid film sells to apply their stuff (protect the brakes from it, but everything else is OK to get it on, rubber, plastic, paint, you name it, and don't worry about getting any on your skin it is lanolin based, though it does look like mayonaise when first applied, and does smell like a wet sheep for a short time after application).
then touch up the fluid film each summer to keep it as perfect as his photo
I did this with my '08 last summer (7 north east winters, near the ocean), which had flash rust all over the entire underside, and it is now black like his (only a few spots were rusted badly enough to stay rusty afterwards, but I think with early doses of film will hold up far better than otherwise).