On the demonstration one's at the market, they put the grease on the pan or oven door, and then use a small blow lamp to make it stick on and look burnt. So it's fresh on grease that day. Comes off easy with any half decent cleaner.
Bought the same stuff at the Caravan and Camping show in the NEC. In the guy's display the caked on grime came off so easily. Bought a load, got it home and it just doesn't work! Rubbish! Don't buy it!!!
Saw a demo at thge NEC, I told my wife not to but it she did. I have tried it on an actifry. It's total rubbish, nothing more or less than snake oil. Don't be fooled by this gimmick.