John has about the right idea -
Spray cans aren't really all that bad - most of them just need to be warmed up first. Here goes............
Wait at LEAST a week (longer is better) for the gloss cote to dry, and carefully sand down the run with wet 2000 grit or finer - takes a long time, but the idea here is that you don't want to add any nasty scratches through the clear into the paint. Once that's done, warm the can and again mist a dust coat of clear onto the model, then another, and work up to a quick wet coat. A polish or wax afterwards often helps, too. Use a really good one, like Meguiars.
Why not practice on a tin can or something first? Having to buy another can of clear is easier (and less stressful) than buggering up the model (do you hear the voice of experience laughing at me?). Get the technique down in your head - dust coats, then quick and even wet coat - but lack of patience is the main culprit for most all modelling blunders (there's that voice again.....).
Future floor wax is a fantastic product - apparently it works well on floors, too.
It's important to airbrush a dust coat of this stuff - it'll make your car look matt - let it dry for a while, then another dust coat, dry, then gradually it'll let you hammer it with a wet coat to bring up the gloss.
Cheers.
Lee Tree