undersealing help or tips needed

Hi guys since its nice weather and all im thinking of getting some underseal on the landy.
does anyone have any usefull tips before i do it like what not to use or where not to put it.
thanks for any help.
oli

hi i have just done my landie i used hammerite underbody seal with added waxoyl - 1st clean all under the wheel arches removing all mud and debris also wire brush any loose corrosion then just paint it on making sure you put at least 2mm on, you can use under wheel arches,door-sills,chasis floor and fuel tanks but do not apply to sump,gearbox,exhaust systems,cables or any machanical parts.

happy sealing