"I am thinking of thinning paint and using an airless sprayer this time. depending on what kind of pine and what grade of wood it can be hard to get it to hold paint or stain in some areas. if there is a high resin content and the wood got heated when it ran through the planer the resin will heat up and seal the wood in areas and will not allow anything to penetrate (large knots or heavy grain can be a" . . . .