Info dumping through dialogue is the same as regular info dumping, but the dialogue explains it.
Since an info dump is a simple explanation, with dialogue you need someone who knows the information, and someone who doesn’t. Here, the knowledgeable person tells the ignorant one (and the reader) whatever it is.
I seem to have misplaced my Eragon book, so I cannot quote the passage I want, but when I find it, I’ll change this. Anyway, in the beginning of Eragon, Brom tells the gathered people the story of the Riders. This whole story is a huge info dump, simply there to tell Eragon and the reader who and what the Riders where. This works the same way as a regular info dump, but in fact more complicated because of the characters required.
The information given could have been told over the course of the book, but instead, it makes Brom seem snobbish and arrogant, since we are told shortly after that the Empire kills anyone who tells the story.
If your main characters are one who would know everything new you have come up with, you’ll need to find a way to explain the rules to the reader. The best way is to show, don’t tell. When something happens, the actions the character or world takes will explain it to the reader. This works better than creating a one dimension character simply to tell the reader. It insults your reader, making you appear lazy and arrogant.
Of course, if a character (like a young child) is present, you can tell them some things. Since most children are ‘full of questions’, allow them to inquire about your world. If you have them asking questions, make sure they ask something the reader already knows, so it is realistic. Even then, don’t do it often.