Most of my floor is pristine, but at the doorway, the dirt is really ingrained into the grain of the wood. I can't get it clean at all with the Osmo Liquid Wax Cleaner (even tried it on some scotchbrite). Osmo do an Intensive Cleaner with the tag line "restoration without sanding". Anyone know if it's likely to clean out the ingrained dirt or do I need to sand it and retreat it?