The problem with spray paint is the low pressure of the can. Try putting some HOT tap water in a bowl the hottest your tap can get. Place the bottom of the spray paint can into the bowl of HOT water. (not to geek ya out but around 120 to 130 degrees is about as hot as your household water can get at your tap.) At my home my water can only get to about 115 degrees.
WARNING:
If you try using boiling water the can WILL explode. HOT TAP water will work well.
Warming up the can will increase the pressure inside the can. When you spray the nozzle will atomize the pain droplets more making a more even spray.
I will not look as good as if you had someone spray it with a good high pressure paint gun but it will however make your projects using a rattle can look much better.
Side Note:
Shake up the can real good BEFORE you place it into the water. It will only need to sit in the water for like 2 to 3 minuets before your ready to paint.
If you are painting a large area, stop an place the can back into the water again to warm the can back up again.
I have done this many times and have had good results. I have also used the hot water from a Polar water dispenser and the water was too hot and caused the can to explode. Made a huge mess and got me in some HOT water, hahahahaha
Anyway good luck