Check with your nearest industrial coatings centre. If you have take the finish off completely, it depends on the alloy used in the bike. Certain metals require a thin wash coat to prepare surfaces for primers. That said, it may just need a clear coat. But in my 12 years and a spray finisher it has been my experience that if it comes in a spray can it sucks! That is unless you take good paint and get a custom spray can. My suggestion is to go to the industrial paint shop and get a two component finish and spray it out of a proper set-up. You may find that the reason you get such a crappy finish is that you are a crappy spray guy! LOL! Seriously, it is an acquired skill to properly apply coatings, more like playing an instrument as opposed to swinging a hammer.
First, prep is everything. Without great prep you will never get a great finish. This means, sanding with a finally primer sand using 400 grit paper minimum.
Second, clean that surface well. Either use a tack cloth or damp cloth but blow, wipe, or rinse the dust off. Tack cloths generally remove some of the static in the bike after sanding.
Third, paint! Now everyone thinks this is easy. If it is soooo easy, why do you think I earn up to $100/hr to do it! Proper equipment is advised. Minimum, air compressor with NO OIL OR WATER in the lines! This usually requires a filter in the air path an a good compressor. you will also need a hose to connect to a gravity fed cup spray gun or better. If you cannot find these tools to use, a custom made spray can will have to do. Custom spray cans should have a fan tip, not the usual round spray like crap tips. This fan tip is usually rotating type to optimize your spray patter. Using a custom can it is MORE difficult to get a clean finish than the above set-up, but not as hard as an off the shelf version. Over the counter sprays are paint. Simply put air makes the paint dry. If you prep the bike first, go to the paint store and get the can made with a 2 component lacquer and immediately spray the bike upon returning home, you might get a descent finish. You must use a two component paint within a specific time limit or it will harden in the can, think epoxy.
It is possible however that the rough finish you are getting is simply because you are inexperienced. One technique required to get a clean finish is to keep all surfaces wet without running until you have coated the whole bike. The overspray would then fall on a wet surface and be absorbed by the wet paint. If you do not keep the paint wet the atomized overspray will land on the finish and create the rough texture you have now that resemble sands paper and sometimes rub off into you hand. The only solutions is to practice until perfect, or get a custom can made with a retarder added. This increases your chance of runs, but will keep the surface of the paint wet longer allowing more time to spray the whole bike wet.
If you have any questions, message me and I will help as much as I can.
