I buy my auto paint ONLY through an auto paint shop. Good paint is not cheap, but the results are worth it. I have gotten immune to sticker shock on high quality paint. (upwards of $500 for an entire vehicle) The one time I cut corners with cheap paint, I hated myself afterwards. The best paint and best sales poeple are in auto paint stores. I recommend no where else.
ps. paint stores tend to be dealers for one of several paint lines. Mine is a PPG dealer and I like PPG products because I know them and am familiar with them. Other brands are as good, or in one case, probably better (and pricier).
pps.A good single stage urethane paint with flex additive for a soft bumper will run you about $100.Be prepared.