I go through a bit of a process on Twitter. If you mean the more rare ones, it's pretty simple. For those, I find them through checking likes. Whenever I visit a page, I scroll through a few of their likes and see if they've posted any good Persona stuff, even if it's not directly Ann-related. If they have, I go to their page, check to see what they've posted, check their likes, and repeat the process. That's how I got the pic I'm posting now.
Otherwise, I just check artists I know are interested in Ann, and then search for certain things. Below are the hashtags I usually search. For some of them, I also search them as a normal search too. That varies depending on what I see get posted. For example, searching RenAnn without a hashtag just gives me unrelated content. Use trial and error to find what searches are giving you the results you want.