The Azek Company tech replied to my email about what paint will stick / hold up well:
" ...........AZEK Trim products do not require paint for protection, but may be painted to achieve a custom color or to cover nail holes that have been filled. If you choose to paint, use 100% acrylic latex paint with an LRV of 55 or higher.
Definition of LRV (Light Reflective Value): LRV is the amount of light reflected from a painted surface. Black has a reflectance value of Zero (0) and absorbs all light and heat. White has a reflectance value of nearly 100 and keeps a building light and cool. All colors fit between these two extremes. Light Reflective Values are given as a percentage. For example, a color with a LRV of 55 means it will reflect 55% of the light that falls on it.
For darker colors (LRV of 54 of lower) use paints with heat reflective characteristics specifically formulated for use on vinyl/PVC products. These paints/coatings are designed to reduce excessive heat gain "
Also advised me that primer is NOT required. Interesting.
" ...........AZEK Trim products do not require paint for protection, but may be painted to achieve a custom color or to cover nail holes that have been filled. If you choose to paint, use 100% acrylic latex paint with an LRV of 55 or higher.
Definition of LRV (Light Reflective Value): LRV is the amount of light reflected from a painted surface. Black has a reflectance value of Zero (0) and absorbs all light and heat. White has a reflectance value of nearly 100 and keeps a building light and cool. All colors fit between these two extremes. Light Reflective Values are given as a percentage. For example, a color with a LRV of 55 means it will reflect 55% of the light that falls on it.
For darker colors (LRV of 54 of lower) use paints with heat reflective characteristics specifically formulated for use on vinyl/PVC products. These paints/coatings are designed to reduce excessive heat gain "
Also advised me that primer is NOT required. Interesting.