Bugs, leaves, and dirt are usually the biggest problem with painting outside. Rain could also be a problem. I wanted to paint my truck, so I watched the weather. There was no rain forecast for a couple days, so I thought I'd paint it then let it dry in the garage. I got half the truck sprayed with a first coat, went in to put more paint in the gun, step outside and it starts raining. needless to say I had to sand it down and start again. As for drying, I'd say hang it somewhere with little dust/ movement like stated before. Maybe do more thinner coats to speed up drying time and cut down on the risk of a bug flying into it.