I've had some doors 'dip 'n' stripped' as the state of the paintwork was terrible. I want to paint them again but I am finding that some areas of the wood must still hold the chemical in them (caustic soda I think) because the paint just reacts and cakes on these areas. They don't look or feel damp still (they've been back in the house three weeks). Any advice please on how to deal with this? - could it be the paint I have chosen - Roseal's knot sealer, primer and undercoat all in one. It's water based - would an oil based primer be better? Thanks