Assuming a keychain already exists.
gpg --expert --edit-key KEYID
addkey and go through process
quit and save
gpg --output my_public_key.pub --export-ssh-key SUBKEYID! (including the !)
gpg --list-keys --with-keygrip to get the keygrip
Add keygrip to the sshcontrol file under the $GNUPGHOME