A few days later ...
Let the ink harden for 5 days and then tried brushed varnish and sprayed UPol clear:
Left to right: 151 Yacht Varnish | UPol Clear #1 | UPol Clear #1 with 151 Yacht Varnish on top.
So varnish still smears it after 5 days, but I could UPol clear the gold pen areas and then varnish over everything.
In theory I should do it cleanly: Fluid Writer and then just varnish over everything.
But I had real trouble getting a smooth line with the fluid writer so I think I'm going to cheat: DecoColor pen with UPol clear over it