Either way will work. Some builders (myself included) prime the wood and let it dry before glassing, to prevent the splotchiness and touchup required when different parts of the wood absorb the resin at different rates. This is not an insurmountable problem, since you can babysit it and reapply as needed to the dry areas, but this can take hours. If absolute minimum weight is your goal, the primer will probably add a few extra ounces, offset to an unpredictable extent by touchup of dry areas. But if the aesthetics of the wood are more important to you, the extra priming step costs only a day each for hull and deck, a few ounces of weight, and a couple dollars' worth of resin, and you are far more likely to get consistent wood color. Hope this helps.