I believe the CFI where I was based said that descending quick (cruise speed almost) should generate enough friction on the leading edge to keep it from icing in those conditions.
Was that meant to be tongue-in-cheek? Almost cruise speed in your PA28 is what-90kts? I've picked up airframe icing descending through cloud in a Saratoga at IAS 180kts. So we know that concorde got warm from friction, flying at Mach 2, but isn't is just wind chill at our kind of speeds?