The instructions for the SamJames cowl call for an interior coating of Epoxy paint. The SamJames folks won't recommend a specific product. What have you used and how do you like it?
Start by thinning some epoxy resin with Acetone and filling the pin holes. Then paint with two part epoxy primer. Once dry, apply heat shielding to protect the cowl from exhaust heat.
I mixed some white pigment in West epoxy to paint mine. If it seems too thick, I prefer to warm the area with a heat gun as l work rather than thin the epoxy with acetone.
Stewart Willoughby, 6 painting.