You can always go through the tags of other fandoms and do the same thing.
The other option is to backtrack posts you like on your dash to other tumblrs. If someone reblogs something you like, see who they reblogged it from. Most tumblrs aren't monolithic. A lot are going to reblog some stuff of their otp, mixed in with all their other fandoms and interests. Find ones with multiple shared fandoms, and then if they're reblogging some quality content of a different genre (vines of cats wearing hats) follow who they're getting that content from.
Tip: You want to check the first two pages of a person's tumblr before following them though so you aren't filled with regret when you realize later that 90% of their tumblr is actually homestuck.
Re: how do I tumblr
The other option is to backtrack posts you like on your dash to other tumblrs. If someone reblogs something you like, see who they reblogged it from. Most tumblrs aren't monolithic. A lot are going to reblog some stuff of their otp, mixed in with all their other fandoms and interests. Find ones with multiple shared fandoms, and then if they're reblogging some quality content of a different genre (vines of cats wearing hats) follow who they're getting that content from.
Tip: You want to check the first two pages of a person's tumblr before following them though so you aren't filled with regret when you realize later that 90% of their tumblr is actually homestuck.