1] scuff the plastic with a fine grit paper or some 00 steel wool.
2] Get any primer, chances are a grey primer best for your silver match. Krylon works fine.
3] Two coats of primer, allow each coat to dry before next coat. Then scuff the primer coats with very fine paper, use the wet-sanding technique.
4] Allow to dry, NOTE~~~~~~~mask off the glass and surrounding areas prior to doing any of this.
5] U need heat for the paint application to bond to the primer. Krylon plastic primer and paint, sold at all K-Marts and Wal-Mart's does a good job.
6] Apply the paint in several coats, do not try to cover in ONE coat!!!!!!!!! Allow each coat to dry before apllying next coat. Take your time, it does not happen instantly for a good DIY job.
7] Ensure you have some heat at each primer or paint application, either sunlight and some decent ambient temp. [at least 70 degrees or more], or use a hairdryer on low setting, and let each coat dry for say one hour.
The only hassle I can think of is getting the silver color to match the ride's color, that is first in the paint color, and then by your visual as you apply paint coats.