Brass is not paint-friendly compared to some materials. But, I have never had much trouble with it generally. Modern, good-quality acrylics do seem to stick better than the traditional enamels, I'm thinking...? Over the years I have used Testors, Scalecoat and hardware store. All have worked; all have failed. Mostly worked.
Always clean the surface well (soap and water, or 409...a good rinsing); etching is good; a primer - plain gray Dollar General stuff - is a step some skip, and I have never understood why they would do that. It's a primer.
