At our shop, we have runs to deal with all of the time. On the large ones, we will use a razor blade at a angle, and slowly cut them down, then hand sand with a block starting with 1500 grit sand paper and water. "Wet sanding" allows for lubrication as you are removing the run/sag in the clearcoat. Sometimes, we will wetsand a second time with a even higher grit sandpaper to make sure all "grooves" and scratch marks are removed as best as possible. Then as stated in one of the previous responses, machine polish with a high speed buffer with a light grade compound, then hand polish with a fine polish for your final step. If you go slow, you will end up with a great final product, just make sure your clear/paint is as fully cured as possible. You will get a ton of opinions about this subject, but this is what works best for our shop, and is only a suggested way of handling this kind of issue. Good luck!!
