Here are three of the current books in the area of plastics
(resigns) I don't know if you will see a class in just plastic
jewelry. You would have better luck with classes in plastic work in
general and then apply it to jewelry. You can check your local Night
school continuing education classes and your community type colleges.
These cover most of what you would need to know to get started.
Along with a great quality dust/fume mask and a good vacuum cleaner
to keep the dust under control. Along with an old school book that
you can find used.
when I recently got mine they a had numerous copies available. Hope
this is some help.
been there and still making the dust fly!