store. The one by my house will mix any paint you want and inject it into a spray can complete with hardener and reducer. Just give them the paint code off your car and they'll make you a pint or quart or gallon of paint. From that they will mix the paint with hardener and reducer then inject it into a spray can. You take the remaining paint with you as you'll have to buy that initially. Later on when you need more paint you simply return with the paint they originally mixed for you and have them make you another spray can full.
