Shameless plug: See also ssb-utils, that has a block/unblock command.

Caveat: these utils are ripe for a rewrite (for various reasons), but I still find them more convenient to use than the lower level sbot/sbotc commands.

If you run sbot on one or more pubs, and if you run a local sbot (e.g. with patchfoo), you can also install the ssb-identities plugin on the local sbot and let it know about the secret files on your VPSes. That way you can locally issue commands on behalf of the remote sbots by using identities.publishAs() instead of publish(). I find this very handy. And one day when I'm bored I will incorporate this in ssb-utils.