I believe I sanded the Paint with 320 grit, but Polycrylic went...400 then 800, then 1500, then I went with those little Micro-Mesh sanding discs...2400, 6000 and ended with 12,000. It was Very labor intensive. After that, I used 3M Machine Polish-Finese II.
FYI...Other than the Paint Sanding...