Sanders:
I think you can use any of the modern two component paints.
I chose to strip everything out and start again. Here’s my vessel sink made from an IKEA salad bowl.
The white walls in the background are done in the POR 15 two-part product called WhiteCoat. It’s porcelain hard and I’m sure it will work on your plastic pieces.
Many more pictures of the Argosy renewal here:
Contemporizing 1976 Argosy D - opinions please
Sergei