I would say to first sand only as much as you need to fair the boat. Rob Macks pointed out that wetting wood will swell it which will help with lots of minor dings, cracks, and holes. I've been doing that a long time...and it does help. Then repair the gaps as needed. If it's big enough to need a wood strip filler...do it. If not...then use one of the other fillers. Usually my cracks are small enough that I don't worry about it until after the seal coat. Then I use a mixture of wood four (sanding dust...not saw dust), flour, or whatever it takes to fairly match the color to fill the small gaps. I sand...but not all the way into the wood...only enough to smooth and level where I filled. I check with water to make sure I'm keeping color consistent. Then...fiberglass the hull. If your strips are the problem...and not the installation...I would mill more for the deck. I don't do B&C. Mine are all rolling bevel, so someone else may have more pertinent information on that type of strip. There is no such thing as a perfect boat.