Add Vagrant ssh_config to docs

morph/grid/local/README.rst

@@ -40,7 +40,24 @@ Build and start the VMs::
 
   VAGRANT_DEFAULT_PROVIDER=virtualbox vagrant up
 
-Then::
+Then, once::
+
+  vagrant ssh-config > ./vagrant-ssh-config
+
+Add the IPs from ``grid.nix`` to the vagrant-ssh-config Host match blocks so the config reads like::
+
+  Host payments1 192.168.67.21
+    HostName 192.168.67.21
+    User vagrant
+    [...]
+
+Then, make morph use this ssh config either - with newer morph - point it to it::
+
+  export SSH_CONFIG_FILE=./vagrant-ssh-config
+
+Or, with older morph, adding the config to your user's ``~/.ssh/config`` file.
+
+Then, build and deploy our software to the Vagrant VMs::
 
   morph build grid.nix
   morph push grid.nix