That is one of the tricky parts of Nostr. Maybe some more relay aggregators like nostr.wine or you could look at some of the relay sites and maybe find some more popular ones? I often have sketchy cell service, so sometime I don't think my notes hit all the relays I have.
Discussion
It should be possible to have a more targeted approach though. Some of my follows are probably not connected to any of the relays I’m connected to. I just need a list of which relays those accounts are connected to so I can have a “complete” set of relays for my follows list.
This is the reason some of the clients are moving to the gossip model, which should fix the issue.