For both eggs and chip fat, soak and scrape repeatedly until it is all off.
I used to do a chip shop which had one small window above the door covered in chip fat. It was nowhere near the kitchen and none of the other adjacent had any fat on them whatsoever. I suspected that the owner (won't say where he came from but he wasn't from anywhere in Europe) was pasting it on deliberately to make me work harder/longer for my bucks. After 2 occasions of pointing out the chip fat to him, and nothing changing, I dropped him.
John