I'm working with a crossover between FiM and Sanchez Chronicles, my own series that has over 7 years of continuity! Plus, with the MASSIVE cast it's kinda hard to fit in some of the continuity, character arcs, the universes, the concepts, etc. so I'm kinda hoping that someone will help me to using exposition to inform people about the aforementioned somewhere between throwing people in blind with no knowledge of who these people are or really absolutely anything and entire chapters being a massive text dump.

What I would do is go over relevant details and descriptions as they come up, to keep information flow manageable, and keep from confusing your reader

1007417 Here are some of your possible tools; use them wisely.

Secondly, as a piece of advice, like the guy above me said, bring up details as they become relevant. Only go into detail about the past interactions of two characters when those two specific characters are together, and even then, if there's a lot to go over, spread it out. Have the two characters bust some heads to hassle a local minor bad guy, and have them banter about old times. Have one character read a news story about another, then show their reaction.