It is enough to apply a white gypsum finish coat e.g. ALPOL AG S22, if the partitions are accurately made and the deviation from plane is not greater that 1-2 mm.. For greater deviations, apply a gypsum putty coat first to level the surface, e.g. with ALPOL AG S19 quick-setting gypsum putty, and then apply (“wet to wet”) a coat of e.g. ALPOL AG S24 ultra-white gypsum finish.