Your best bet, is to go into a auto refinishers and ask for the colour you after (know what you want thou, if you go in and ask for a can of range spray paint they won't be best pleased, I never am when we get knobs in at work asking for a can of red.) Ask for a can or 2 of high build primer, and 3 cans of the colour of you choice, and 2 cans of 2 pack lacquer, thats suitable for the paint. Strip the frame back to bares, and give it a good sand down with some 240 grit wet and dry or the like. When your happy with that then heat the frame a little with a hair dryer all over and give it its first light coat of high build primer. The idea of high build primer is to hide all the little imperfections, obviously your not going to be filling dints with it, but its a lot easier to work with if you want a great finish. While its drying go over it with a hair dryer until its totally dry. Not touch dry it needs to be totally hard paint, again, give it another light coat of high build and flat it between coats. Your best bet will be to go for around 3-4 coats of primer, depending how good you are at flatting your paint Then its time for the colour, give it a little heat treatment before you start as this will replicate baking the paint, it won't be anywhere near as good, but it's the best you'll manage on a home job. Same as before being light coats is the key to a good spray job, your first coat wants to near enough just dust the frame, then repeat, your frame should be totally covered by about the 3rd coat, then its up to you how much paint you apply! The more coats you apply, the harder your paint will be if applied well. after this your best of leaving it over night, for the toxin's to come out of the paint, before you apply your coats of lacquer. With the lacquer its the same as before with taking your time and light coats being the key. Heat the frame slightly (not to much, as the lacquer will dry as it lands on the frame, and will leave a rough texture that will look flat and dull) between coats, give it a good 30-40 mins of drying time, as well as a few minutes of hair dryer to help it dry hard. For the best result, use about 3-4 coats of lacquer, as anymore won't really do anything to be honest on a bike frame. If your applying stickers or anything afterwards, your best off to leave it a week ro so, just to be sure your not trapping toxins under the graphic's! The comment about 'there isn't professional canned spray' What do you think it is? Spray paint is the exact same as what a prof. sprayer will use, just with air dry additive in the paint opposed to hardener. As you have all said, the finish is in the prep!