I no longer have a PBC, but I used to take a stiff plastic putty knife and scrape off the excess gunk. What didn’t come off was fine with me... I just considered if “seasoning”. From time to time, I’d also leave the lid cracked after a cook and let the fire get pretty hot for about 20-30 mins to kind of burn up some of the gunk. Not blazing hot to the point I was damaging the cooker, but hot enough to the point that the greasy underside of the lid was pretty dry and crusty. Made for easier scraping.