with a good knapp roller and pour in a light mix of texture...if it is already not totally smooth. This would be simplest if you think just painting the exisitng surface will not look well. If it already has a lot of places that are not smooth due to the adhesive used to apply the acoustic tile. IF it were me I would just paint it with a good roller and add in a light mixture of texture to your paint...applying both as you paint That whould look fine. Good luck LJ