Flushing rewrite rules on plugin network activation

I’m working on making a plugin compatible with Multisite. Currently the plugin adds a rewrite endpoint and runs flush_rewrite_rules( false ) on activation.

This only flushes the rules for the primary site. I have successfully added the endpoint and flushed the rules for new sites created by hooking on to the wpmu_new_blog hook.

I was thinking of looping through all the sites on network activation and deleting the rewrite_rules option, but I don’t think this is the best way. I already tried calling flush_rewrite_rules( false ) within the loop, but it doesn’t seem to be foolproof.

Is there a better way, or best practice for doing this?