Yes a thinned coat of emulsion. Never use PVA as it may cause some problems. Below is a copy of an e-mail from Dulux on this issue, it was sent to someone on another site a few years ago.
This e-mail was received from Dulux about putting PVA in with the first coat of emulsion or applying to walls as a mist coat.
E-mail I got from Dulux trade asking them for their opinion on the matter (previous thread)
Thank you for your E-mail I can categorically confirm we DON'T recommend using PVA to seal new or bare plaster. This is because the PVA will seal any residual moisture on the plaster and may cause bubbling when it dries. This is also stated in the BS 6150 and our ICI site work instruction.
Hope this helps.
Omar Amjad, ICI Paints Technical Advice CentreICI Paints, Wexham Road, SLOUGH, Berkshire. SL2 5DSPhone: +44 (0) 870 242 1100Visit our web site at
http://www.duluxtrade.co.uk