How does introducing federated communities work again?

Sorry, newb fediverse question:

For example, I can browse here through sh.itjust.works/c/general@burgitt.moe just fine. But I can't seem to browse, say, animemes@burgitt.moe. I think I read that a user on one instance has to attempt to browse a community in a federated instance, before it will appear on the first instance? But animemes 404s, while the federation clearly works because I can see general. Does it just take some time?

I'm just trying to get an account which is on a well-federated instance. I want access to posting free-speech instances like burggit, but I also want access to post on mainstream instances like lemmy.world which defed burggit. I actually started on lemmy.world but switched to sh.itjust.works after looking at which their defeds were (literally just burggit lol).

For that matter, if I want to find burggit communities that are new to me, am I mostly stuck browsing the burggit front page, which means I'm logged out of my sh.itjust.works account?

What I really want is a good way to browse an instance's local front page, theme and all, while being logged in on another instance and still able to vote and post. I guess that's going to come in the form of some app/browser extension we don't have yet though.