I have always done my painting outdoors. NOT because I want to, but because I don't have access to a garage or other suitable building.
I have had pretty good success and lots of compliments on a job well done, but there are drawbacks:
1. You must have a day when the wind is not blowing or at least is minimal.
2. Don't park your car/truck in direct sunlight. Even on a seemingly cool day the direct rays from the sun will heat the metal and cause the paint to dry too fast. This will cause dull areas in the paint job from overspray not being able to "melt" into paint that has already dried from the heat.
3. You will get some bugs and other debris in the paint job, simple as that. When painting outdoors it cannot be avoided, so be ready to accept this fact.
4. Remove all masking tape from the vehicle as soon as the paint is dry enough to allow it, usually in about one hour. Just be very careful because the paint will still be "soft" at this stage. Anything that comes in contact with it will leave a mark. If you leave it on longer than necessary, you will end up with a sticky mess to deal with later. Tape adhesive and sunlight do not go together very good.
5. DO NOT paint in the evening. Start as early as possible so the paint has as much time to dry as possible. If you start too late, you run the risk of dew falling on the paint before it has time to dry properly. Not a good combination. I made this mistake about 20 years ago when I painted my brothers Camaro. The paint was a bright red and looked really good when I finished. When we went out the next morning to look at my handy work we were shocked to see that the hood, trunk and roof were now pink. After it sat in the sun all day most of the "pink" went away but not completely. That is a lesson I have never forgotten.
7. Even though you are painting outdoors, you still need to wear proper protective gear. Paint fumes and overspray goes everywhere so be safety minded for yourself and others around you. Keep everyone else away while you are painting, especially children.
You can get a very nice paint job if you do it outdoors but just remember, it is just that, an outdoors job. It will never be like a professional job no matter how good you are with a spray gun or how careful you may be. There are too many things against you that you have no control over.
Hopefully these tips will help and if I have left anyhing out (or mis-informed you about anything) I am sure that MARTINSR will be able to clear it up. GOOD LUCK!