Any matte surface is a dull or unpolished surface. Matte is just another word for dull.
P4000 grit, unpolished, is usually the first step in smoothing out a too flippy 1500 grit polished surface. You may wind up taking it to P3000 or P2000 grit in the end. It depends on both how flippy it is and what your ball speed.
I'd suggest sanding it to P1000 grit to remove the polish, then P2000 grit pad, then a P4000 grit pad to get it to a god starting point.
(FYI if the surface appears shined even slightly after using the P4000 grit pad, then the pad was too worn and was not at P4000 grit. Then you need to take a fresh P4000 grit pad to correct that surface.)
Good luck.
"None are so blind as those who will not see." "Some bowlers are crazy as pickled cats."