Among the many painting tips already posted here on TRF, the approach that stands out to me is:
1-- Use appropriate masking tape (regular tan "masking" tape may not be the best, should try blue "painter's" tape or even artist's trimmable gasket/masking material)
2-- First spray should be a light coat of CLEAR paint on the edge of the masking to help seal any gaps
3-- Follow-on color coats should each be light (attempting to get all the color onto the rocket in one heavy, drippy coat usually doesn't work out well)
4-- Between each coat (either clear or color) wait either an hour or so (for the paint to set but still be ready for another coat) or wait a couple days (for the paint to reach "bone dry" condition)
5-- Use paints that are compatible with each other (same brand, style, etc) for primers, clear base coats, and color coats; test your paints on some scrap if you have any doubts
6-- Don't get in a hurry, if you are working for a "nice" finish; slow is fast