Hi James,
I have painted my bumper twice during my ownership.  Once in 2015 in St Martin and just last week.  Each time I used a can of acrylic spray paint acquired at my local big box store intended for plastic yard chairs.  I found it to have excellent adhesion.  I simply sanded with 220 grit, cleaned and sprayed multiple coats.  The paint lasted 4 years before wearing through.  It did not flake or crack and cost less than $5. even in the Caribbean.  I was also able to find a excellent color match to the slightly off white Amel hull.

Will Stout
Anni Bea True SM 180
For Sale in Annapolis, MD.