Make Your Own Paint Spray Bottle

How do they work for big panels? I have 2 doors to paint.
I sprayed a fender on my Trans Am back in 1991 using one of these. The paint went on OK and I did it with a single aerosol unit, but don't expect spray-gun results. You'd need to color-sand it a little before buffing. It's not really orange peel, it's just not perfectly smooth. The guy to whom I sold the car crashed the balls off it about a year later, and no paint jumped off. I still have a piece of that fender in my garage.