I think you overKILZed with the primer. One coat of primer is usually sufficient. The orbital might be a bit too aggressive for sanding. Use a 1/4 sheet palm sander with 220 grit. You can use oil or latex paint for your topcoats. As far as the foam roller, I am not a fan. It holds very little paint and will leave skid marks in your finish if you're not careful. A Whizz roller with a mohair roller sleeve leaves a nice finish. You can also use a regular Whizz roller sleeve, because the mohair can act a lot like the foam roller.......it holds very little paint.