:( finger mojo
I guy I used to work with (since retired) gave me a can of some kind of slippery paint-like stuff to put on the underside of my Honda lawnmower right after I had bought it. Using a paintbrush I applied it liberally to the mowers underside, and now, even four years later, the grass doesn't stick.
Not sure what it was called but he said you could find the stuff at Tractor Supply Company.