Specialty spray paints can be found in most decent art supply stores and even have stores of their own. Although if you live in a major metropolitan area most times such stores will be located outside the city limits. For example, we took a 20 minute trip from downtown Chicago out Oak Park to such a store to buy some of their supply in person. Sure you can look at websites and order things online, but sometimes it's nice to check colors out in person. You can also purchase markers with the same ink for creating your own wall art!
Advantages to using higher end paints is 8/10 times, all you need is one coat (after all they were engineered to be used on the fly on the streets). The exception being some of the lighter or metallic colors, but even then, one pass will usually get the job done.
You can also purchase different caps for your spray paint. Changing your caps allows you to change the width of your flow (that sounds dirty huh?) making back and forth quick sprays a thing of the past. Covering large objects without heavy overlapping streaking has never been easier! You can usually pick up a pack of caps for under $6, but if there's a type you like more than others you can order them in bulk.
The sky is truly the limit and we love having a few cans on hand for projects we want to give a little more pep too!
Here's a few places to try when looking for specialty spray paint and supplies: