Clay bar it. From Meguiar's site :
After you wash and dry your car, run the palm and fingertips of your clean hand across the top surfaces. Don't be surprised if what you feel is rough and bumpy. The roughness you feel is the presence of harmful environmental bonded contaminants such as over-spay, fallout, brake dust, tree sap mist and more that have bonded to your paint finish. Most of these contaminants will wash right off if immediately addressed, however, others bond to the finish and week by week, if not dealt with, will gradually mask and blur the reflection. To remove these bonded contaminants and bring back that "smooth-as-glass" finish, this will require an extra step, prior to polishing and waxing, commonly referred to as "claying". By utilizing Meguiar's Smooth Surface Clay Kit, you can, in less than 30 minutes, clay an entire vehicle, giving it back that "smooth-as-glass" feel… and properly preparing that surface for a quality coat of wax. By doing this, your car will not only feel incredible, it will ensure the wax that you apply is able will be able to function properly.