Claying is done to remove micro contaminants which settle on a vehicle. So typically you clay the horizontal surfaces rather than the vertical surfaces. If you have visible substances on your paint, claying probably won't do the job. I would soak a microfiber towel in car wash soap and leave it on the area for awhile to see if that loosens it.
But if you decide to clay, here's my technique. Remove your ring(s) and your watch. Moisten the clay and spread it out over your palm between the little finger and thumb. The little finger and thumb actually touch the cars surface, so you can feel the proper pressure. Wet the area. Work in a small 2' by 2' area at a time. I use water but they make a clay lube as well. Only work the clay in a back and forth lateral direction along the length of the car. No swirling or side to side motions. You're done with the area when it's smooth to the touch. Keep the area wet and fold the clay over and rework it as you move to a new area. You typically only need to clay the horizontal surfaces where contaminants settle. When you're done claying, rinse the car, dry it, and apply a wax.
mwalsh wrote:Despite a good coat of wax a few months ago, my hatch feels nasty and rough, and I've got some specks of Lord-knows-what stuck on the paint harder than I don't know (they certainly don't come off with washing). Anyone with clay bar experience care to share some techniques?