I enjoyed a book called Babylon: Mesopotamia and the Birth of Civilization by Paul Kriwaczek, but was surprised near the end by the author's assertive retelling of Persia's capture of Babylon:
Cyrus had devoted great effort to psychological warfare. Months before his invasion - perhaps even years - his representatives ha been busily spreading the word that the Babylonian King had proved himself a menage to his neighbours and an oppressor of his own people; that he must be deposed to restore freedom and justice to Babylonia...Agents were dispatched to loiter in the bars and taverns to encourage the disaffected citizenry to abandon their loyalty to Nabonidus and to welcome a new ruler who would restore all the ancient traditions so neglected by the usurper of the immortal Nebuchadnezzar's throne, and deliver mercy and fairness to all."
The author's bibliographic notes don't seem to cover this section of his writing and online sources were not too helpful. I did find some general talk of Cyrus' exploitation of Nabonidus' unpopularity, e.g. on this AskHistorians thread, and I think it is well known that Cyrus gave promises to disadvantaged groups, such as ending the captivity of the Jews. I also found an article on the mixed perception of Cyrus has a great liberator vs. torturous despot, however, though it casts light on Cyrus' potentially overlooked traits, it does not talk about any "psychological warfare."
I wonder what his source for this is; I can't find anything of the sort in Herodotus (who devotes relatively little time to the Babylonian conquest). There was a theory popular once upon a time (maybe 50 years ago) that the author of Deutero-Isaiah was a Persian propagandist drumming up support for Cyrus' conquest of Babylon. But it's not like there's any direct evidence for this "psychological warfare".
This part:
spreading the word that the Babylonian King had proved himself a menage to his neighbours and an oppressor of his own people; that he must be deposed to restore freedom and justice to Babylonia
certainly matches what Cyrus says in the Cylinder, but said cylinder was of course only produced once the conquest was over.
The fact of the matter is that we just don't have the kind of records we would need to say what kind of strategies Cyrus used, hell, we can't even establish much of a timeline for his life. Entire decades are filled with question marks. So, the author seems to be engaging in some fanciful speculation there.
Otherwise, I think /u/Tiako 's answer that you link to sums up what little else can be said on this particular matter. I will note for the record that I disagree starkly with the views they (and /u/Daeres in a linked thread) express on Zoroastrianism, though - the Persian kings from Darius on (Cyrus is sketchier) were most certainly Zoroastrians. The view that they weren't is very fringe among specialists on Zoroastrianism these days. I think it sometimes lingers with those who specialize on other areas of the Ancient Middle East due to outdated perspectives on Zoroastrianism as a religion. Not the more vibrant field, unfortunately.