Mainly as you said with brute and glob but also how hector hall and lyta hall are seamlessly interwoven into the story and how central lyta halls character becomes.
Another is Wesley dodds and his story (the original 40’s sandman) was integrated as well. It was explained that since Dream was trapped, that the universe tried to find someone to fulfill his role so Wesley Dodds began having dreams subconsciously telling him to do Dreams job. Basically it explains why he existed as the sandman in the 40s within the dc universe.
Characters from the House of Mystery comics actually comprise more of the main characters than you would expect. Lucien, Cain and abel, and even Matthew, Dream’s raven is a character from Swamp Thing who died and is reincarnated as a raven.
Theres alot more but those are the major callbacks off the top of my head. Gaiman really liked putting lesser known dc characters in his story and pressented them in such an original and unique manner that alot of the time you dont even realize they are callbacks.