(Disclaimer: I've never tried to move large numbers of people off of Facebook; I have organized community groups from scratch before, and I have led initiatives at work that consisted largely of convincing people to do a thing. Much of this advice is from that perspective. YMMV.)<p>So: my advice is to not think of it as all-or-nothing. You will <i>not</i> be able to move 300k people off of Facebook overnight. This is somewhat akin to every IT migration project ever: it always takes longer than you think, and is not always a linear process from "fewer people migrated" to "more people migrated".<p>It's also akin to community organizing: there is no substitute for actually talking to people about it, especially in the initial phases. Or: high-touch sales, where you may initially need to spend a <i>lot</i> of energy and time per person successfully moved over. The other common thing here is that you will hear "no" a lot, which is a valuable experience anyways (but will be frustrating).<p>Also: unfortunately, no one will care if it's self-hosted or federated, outside of niche tech circles. They will care about whether they can reach the people they want to reach, and whether the user experience is good or not. This is reality: talking about these points <i>will not help you</i>.<p>Some things you'll probably need to do:<p>- Identify a single credible alternative platform.
- Identify specific groups of people who are willing to be early "de-adopters". For instance: a local youth group, a sports club, whatever. Ideally you are a part of this group already; you then have a much better chance. Businesses will likely say no, so you want community groups.
- Within those groups, identify champions: people who care about the same thing you care about, and are willing to commit time and effort to help.
- Together with your champions, build a toolkit that allows you to scale up your efforts. This may be guides on how to talk to people about the change - what works, what doesn't. This might be instructions for setting up a specific platform. It might be communications channels, leaflets / flyers for putting up in public places, whatever.