DIY & Home Improvement

http://www.krylon.com/safety/surface-preparation/

When working with plastic
For old plastic, use an ammonia-based cleaner and wipe down to clean surface. If the plastic is new, wipe down with paint thinner for best results. Lightly sand glossy surface if previously painted and remove dust with a tack cloth. When dry, apply Krylon® Fusion for Plastic according to the directions on the can.
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I paint one gallon juice bottles with Krylon® Fusion, fill them with water and put them in the garden. I have a few that are three years old and have all the paint still on them.