Clay bars are used to remove the dirt, grime and other rubbish which you may not be able to get rid of by simply washing the car, such as tar spots etc. You would use the clay bar before touching the car with a DA and after washing and drying.
If you head over to Halfords or speak to Howie on here, you'll see that they usually come as a starter kit, the actual bar and a lubrication fluid (quick detailer usually). There's a certain technique when using them where you need to keep the surface lurbicated so the clay bar slides over the surface removing all the crap but this is fully explained in the instructions sold with the product.
The main difference you'll get is the overall feel of the surface (which will be smoother than a babies behind) and you'll relaise that the car you think its lovely and clean.....actually has a mountain of crap stuck in the paint......I know i did lol
If you do decide to try one, I would go ahead and buy the Meguiars clay bar kit. It comes with the bar, the lubrication fluid and a microfibre towel i beleive but if you speak to Howie; I'm sure he will help you out
by the way - I'm no expert when it comes to products or paint care so if you want some more help, I would speak to either Marc S or Howie on here who will be able to help more
