rust proofing??

just wondering does anyone do this to the underneath of there car.... and whats the best way/ products to use.
Should i get the underneath power washed and then just wd40, should i use waxoil.... or should i get under with a wire brush and some black spray paint.... any sugestions appreciated

wire brush,
elbow grease,
black spray, (is it called shultz or something?

thats what my mate did to a fiesta.)

Best thing to do is give underside power wash to remove heavy dirt/grime... then give and surface rust on underbody a rub down with light grade sandpaper or wire brush. Best product to use is Dinitrol or Schultz undersealer which can be bought in an aerosol or in cans for spraying with compressor and special applicator gun. Any good motor factors should stock this... if not try J&S on York Road in Dun Loaghaire or Frost who are online and based in the UK. It's good ould dirty job.... plenty of old clothes and face masks required!!!

cheers lads... any place (other than exhaust) that i shouldnt paint this stuff on???

Try and avoid your diff... any plastics... shocks... drive shafts... prop shafts! You basically only want to cover the underbody panels and maybe your subframes!!! Make sure to get up inside the lip of your arches after clearing any caked in mud out of there!