Ah yes, I thought I'd be using the trusty route add command.
Each of our locations has a different subnet on the 192.168.x.x scheme. The one I connect to is 192.168.134.0. I'm quite happy to just make a blanket route for all 192.168.0.0/16 addresses to go through VPN. The only thing is that our router here (a Linksys home router) allocates IPs on the 192.168.1.0/24 network. How do I add that route properly?