This article describing how an actual, high-end, union organizing campaign works should be mandatory reading for all HR managers. It provides a chilling account of how effective union organizers can be in subverting a company's workforce, even with (or perhaps especially with) highly skilled and educated employees.
It also demonstrates convincingly how much of an advantage union organizers have even without the new "fast-track" regulatory modifications currently proposed by the NLRB. Those modifications are specifically designed to curtail company's ability to counter the union campaign, and tilt what is already an uneven playing field further in the direction of the union.
Pay particular attention to how this particular organizer used peer efforts to tar the neutral or pro-management employees with the label "traitor", and how readily the union was able to access company information through the efforts of pro-union employees.