Think about this. If you could get away with never cleaning the BBQ Grill, would you? The best way to clean a BBQ grill is, simply, don't. You can for sure get away with that if you're using the best BBQ accessory for this purpose, BBQ Grill Stones. They block the runoff and residue from contacting the grills so cleanup is done on the stone which is quite easy. You don't scour the stone- it cures like cast iron.
The best way to clean a BBQ grill is to avoid the need.