I just finished painting a bike..the second of two bikes that I've painted, so far. I use PPG auto paints loaded into rattle cans. This offers you hundreds(thousand+?) of colors. Auto parts places that sell paints will have a machine to load spray cans. I use Buy-Right Auto Parts in Racine. The basic process (for me..there's many) is 2k SprayMax primer, base coat color, 2k SprayMax Clear Glamour topcoat in high gloss. This yields terrific results for about the same as you'd pay for a powder-coat job and looks MUCH nicer. Easy paints to work with. Wear a chemical mask. Spray around 70 degrees and 50% humidity, outside preferably with little to no wind..pick your days. Make sure the various paints you use are compatible or you'll get to strip and paint the bike twice.
Just took a few not so great phone photos. Frame and fork looks much better in person. I didn't do the sanding between coats as Doug suggests. Doug's process is the correct way to do it and no doubt yields a flawless paint job. My paint jobs, while not perfect, are a 1000% better than what I started with (the bike pictured here was a pukey blue color, emphasis on pukey, and was about the ugliest bike in the world.) and I'm good with a couple tiny flaws. If I had a more controlled painting area rather than outside in typically hot and humid, and often windy Wisconsin summers (I'm right by Lake Michigan), I'd probably spend more time in the process. That, and with so little experience, and not wanting to repeat any of the (good) results I've achieve on a paint job in progress, I'm a bit afraid to mess something up and have to re-do priming and/or basecoat and/or clearcoat. The paint runs about $25-$35 a can. I use one can of 2k primer, two cans of basecoat-main color, one can of basecoat accent color, and two cans of 2k clear glamour coat per frame/fork. All in..the red frame was $180 in paint.
The blue frame pic is a bike I painted last fall. Same paints, same process, but before clearcoats. The pinstripes are uniform-straight..just distorted by the camera.
edit..The red bike is inside my truck. Auto paints are often baked after application. Since I don't have an oven that size, I'm letting the frame sit in my truck as it gets plenty hot in there when sitting in the sun.