or do you pva it or summat?

 

No just thin some paint down wit water and do an undercoat with that

 

as above, water down the first coat, as it will get sucked into the plasterboard straight away, but yes you can.

 

depends on the type of plasterboard, if its just normal wallboard or similar you are best to seal it first or use a watered down coat as above, but you are fine to paint straight onto it! are the joints taped and filled?