Yes, that is exactly how you do it. One can have multiple keys in .ipfs/keystore.
Those additionally generated keys are not tied to a node (which has a separate, “identity” key on its own).
One can copy one of those keys to a different node and publish to the same ipns from there. 
(Some time ago I did PoC for publishing with the same key from two different nodes using HTTP API, so it really works)