you "rub" the clay along the paint and it really picks up a lot of crap from your car...you may be surprized...especially with out 10 year old factory paint jobs(those who havnt been repainted) wash the car real nice, (id use dish soap cuz the clay bar is just gonna take the wax and what not off the car anyway) and follow the directions that come with the bar...it may SCARE you how much dirt that thing pulls off with it...i washed my car real well before i used it...and by the time i was done with the hood and fenders, my little blue clay bar was BLACK with dirt....
....just did it on my girlfriend's 2000 Focus and it wasnt so bad.....
Anthony