I have been refinishing floors in Cape May New Jersey at the Southern Mansion. Please check web site SouthernMansion.com to see pictures. The flooring in the Mansion is oak, and hardwoods. I am having the same problems and have contacted many different people. The wood fillers, DAP, plastic wood, etc are fine on smaller areas but do not expand and contract witht eh weather so they crack. I to am looking for a flood mix that can be sanded and dries quickly. Boat Life a marine product can be used but takes 24 hours to be tack free and 7 days to cure. It comes in a tube and about six different colors. I am doing a floors 3 to 4,000 sq ft and a tube to fill cracks would take about a month. Too much down time. But this product does work well for small floor areas. Any good marine store can get this product or check the Web at www.jamestowndistrubuters.com in RI.