I have just had the tank removed from the airing cupboard and am trying to emulsion the old bare plaster but it will not cover what shall i put on first
(1) buy a massive tub of cheap magnolia paint.
Dilute it about 50/50 with water.
Paint your walls with a fewf coats - this will prime them nicely.
remember to allow time for each applied coat to dry before applying the next
or
(2) you can buy universal primer sealer to apply to bare plaster
any good local DIY shop or store will stock such a primer sealer