Buy quailty primer, paint and lacquer, preparation is everything. When you start strip as much paint off as you can, cut the alloy with wet and dry starting with P150 to get rid of any corrosion, then use finer paper P240 and then P600 to lose any scarring caused by the P150, this is where you can see the finish. Now mask up anywhere you don't want paint. If the metal looks good and smooth here the finish will be good and smooth, all the spray will do now is accentuate this surface.
Next apply about 6 light coats of primer. Golden rule: TAKE YOUR TIME!! Let each coat almost dry so it's ever-so slightly tacky. Use your finger nail to try how wet it is by tapping it gently, NOT YOUR FINGER PRINT SIDE, this way you'll only leave a smooth indent rather than a ridged fingerprint. When spraying keep the can moving and don't start or stop when above your wheel.
I find that if I start spraying the colour as the last coat of primer is still drying works best. Put about 10 lights coats of your choosen colour on in the same way you did the primer. If there are any imperfections such as dust, flies or nail marks NOW is the only time you can remove them. Use a P600 or P800 paper to remove them by rubbing in circles not back and forth and then spray again.
All paint from a rattle can at this point looks the same to me. If you can't finish the wheel/item you are working on the day you started it or the paint dries out(overnight for instance, bare in mind the paint will take about 3-5 days to cure properly) cut it with P800 paper then put another 2 coats of paint on, then start your lacquer.
I'd put about 8 coats of clear lacquer on. Once again, TAKE YOUR TIME. Everytime you lay a coat down make sure nothing touches it!! By now you should know roughly how long before it's tacky to the touch SO TIME IT rather than touch it. Once you've finished spraying put the wheel/item out of the way of anything that can touch or land on it. Leave it a minimum of 24 hours before removing any masking.
ABSOLUTE PLATINUM RULE: Do not, no matter what, do this in your kitchen!!!! I did 3 years ago, since then even though we've moved house(not because of this but still)as soon as I even mention painting I still get told "NOT IN THE HOUSE". Women, mine especially, just don't understand when a set of rims need painting and it's raining it's obvious you'll do it inside!!! Personally I didn't get what she was so upset about? I mean I'd even put newspaper down and everything!! Still, she was very unhappy with me for quite a while!!