^ you need a lubricant of some sort for clay to be effective (otherwise you're effectively rubbing dry clay onto paint). The liquid clay bar is a type of all-in-one method where the "clay" is already in the solution (shake to activate) and you're just using a foam pad to apply.

Here's the thread in detailing with a referring link about clay: http://www.xoutpost.com/detailing-for...t-exhaust.html

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'08 X5 3.0si - Alpine White / Saddle Brown interior
Specs: Sport Pkg, Premium Pkg, Tech Pkg, Comfort Access, Aero Kit, Style 433 staggered 20s on Conti DWS
Mods: Carbon 35 tint, LED angel eyes, GP Thunder 7500k fogs, H&R 20mm/25mm spacers, clear reflectors, gunsmoke-tinted taillights
Coded: Digital speedo, windows/sunroof/tailgate close via keyfob

X5 pics at Flickr