Painting flexible plastic

You might also look at automotive paints for plastic bumpers & other flexible parts.

Hi ;

 There is a product marketed by Rust - Oleum . It's made for vinyl furniture and patio pieces .It might work .They say you can spray it right on with No Primer !  T.B.

If it is either vinyl or polyethylene, good luck.  Paint adhesion to polyethylene is terribly poor, and with vinyl almost any paint reacts with the plastic and stays gooey forever.  There are folks I know who paint it okay, but they use a special primer- I forget now what it is.