...the old fashion rattle can is the cheapest. try the "dupla-color" brand. you can find it at most any auto-parts joint. it's made to repair car paint.
...don't be afraid to remove parts from the scooter to paint. you'll probably still need to mask off lots of things so have some good masking tape and a razor blade for detailing... DONT RUSH IT!!! take your time and make sure the paint is dry before handling... most paint jobs get fucked up because people have no patience... several light coats is the key...
rustoleum and krylon are also excellent paint brands. pick a primer and clear coat that is the same brand of the paint... some formulas don't like each other... spend some time with your color choice...
proper prep work goes along way... i don't recommend 'sand blasting'. a good sander and steelwool should do it for most jobs... you don't need to take it down to the metal...
good luck and send pics of before and after, if you can