When a neighbor doing some spray painting got some paint spots on my car, I first tried removing them using a razor scraper and water.  This worked, but it was pretty time consuming, and required a lot of care, so I decided to try Mothers California Gold clay bar kit.  The kit contains two bars of clay, a microfiber towel, and a spray bottle of Showtime Instant Detailer.I found that while the clay product does a pretty good job of removing dirt, sap, and small particles, adhering to the paint finish, it doesn't do much for removing paint spots.  For the uninitiated, using this product effectively requires developing a certain technique, particularly if you have a thick layer of gunk on your finish.Firstly, the surface you are treating should be cleaned of surface dirt, and cool.  The Instant Detailer spray is pretty slippery, and there is very little friction when sliding the clay bar across a surface sprayed with this stuff.  What you want to try to do is have a thin layer of the Detailer solution on the area, so you can slide the clay over the surface, but still get enough friction so the clay can pickup and remove particles from the finish.  If you have never done this before, it may take some trial and error to develop a technique that works.Since the clay is soft, it is constantly changing its shape as you use it, and from time to time, you will need to reshape it.  One thing to be very aware of, is not getting any debris into the clay.  If you accidentally drop the clay on the ground and happen to get a small rock, piece of metal, or other hard substance stuck in the clay, you could do some major damage to your finish, if you use the clay.  I store the clay in a small zip lock bag, and always be sure to have a zip lock with me when working, to try and keep the clay from picking up something that could be destructive.The bottom line is that the product works pretty well, but you will probably need to have a decent technique, and plenty of muscle to get the job done.  The process is not a simple spray on and wipe off, it will require some time and physical effort to do an entire vehicle.  The clay works on all kinds of finishes, but probably produces the best results on smoother finishes, as there is less friction.  Prices for automotive accessories at Amazon fluctuate and aren't always the greatest, so check locally for your best deal.  Hopefully this review was helpful.