In priming soft wood, the paint should be applied with a full brush and enough paint used at all times to satisfy the surface. It should be well brushed and especially on the harder grain to assist or force the paint into this close grain and remove by hard brushing any surplus paint that remains on the surface.
On hard or close-grained wood a medium full brush should be used in applying the paint, as this class of wood does not possess the absorbing properties of softer woods, but requires more brushing in order to force a sufficient amount of oil and binder into the wood and at the same time not leave an excess of paint on the surface.
If the priming coat is of the proper consistency, carrying sufficient pigment to fill and hide the grain, and well brushed into the grain of the wood, most of the absorption will have ceased with this coat and no excess of pigment left on the surface. This thin coat will allow the second coat to penetrate through and satisfy any part of the wood which was not fully filled at the time of priming, also allow the second coat to bind itself to the wood and priming coat.
An excess of paint on very porous woods will cause peeking or chipping. This heavy coat prevents the oil from penetrating the woods and assists in holding the coat on the surface. The oil and binder in the second coat penetrates into this heavy coat only and does not reach the wood so as to assist in forming a solid coat well bound to the surface.
Paint heavily applied to a hard or close grained surface will dry with a gloss, forming a hard glaze over the surface, into which the second coat cannot penetrate to any depth; it will only fasten itself to the outside of this glaze coat, whereas it should go through to the wood so as to help strengthen the second and subsequent coats.
Do not prime a building and allow it to stand any longer than is necessary in order to thoroughly harden the paint
