hi guys just skimmed a wall of which i had put a coat of bonding on the day b4 ... i give it 2 coats of pva 1st coat let dry 2nd coat to tacky then skimmed it but the whole wall came out in the dreaded air bubbles ... any ideas has to why or how to elimate this ... my pva was mixed at 4-1 ... wall turned out fine in the end but had a few anxious moments