I went over to the toystore (Home Depot) to pick up one little supply item – and once again found myself in the tools section. They had one of the big hand planers on sale; I didn’t have one, and I know they should help leveling out the warbles, so I grabbed it. It seems to chunk up the foam quite a bit. Is it possible it came with a dull blade, or is there some technique to it?
Sounds like a dull blade. Cheap planer maybe?
Virtually every tool with a “knife-type” blade on it comes from the factory needing final honing. The exception is carbide-tipped cutters. They are already sharp. Consider buying carbide cutters for your planer. They last much longer than high speed steel.