Perhaps not in the way you think.
Let's say we are painting with spray cans, and let's say we have already properly prepared the part by sand blasting, wire brushing, or other methods of removal on old paint.
Now it is time to paint and here is what you need:
After you prepared the part for paint, it needs to be clean and free from any water or oil. I've had great luck giving the part a quick wipe with a solvent such as mineral spirits to remove any oil followed by a wipe of alcohol on a white paper napkin or towel.
If there is any dirt remaining on the part it will readily show on the white napkin and you know the part needs to be cleaned again.
You need to heat the spray paint can. You can put it in a bucket of hot water or you can blow hot air on it. Either way, you need the can warm to the touch. This helps mixing of the contents and it increases the pressure inside the can. More pressure makes a better spray pattern and less nozzle clogging.
What is wrong with this picture?
Paint manufacturers recommend spray cans be stored top down.