The would-be communicator of brewery knowledge could operate by publication, by private instruction or by selective combination of the two. Each approach carried both opportunities and dangers for the promoter's credibility. Publication, as illustrated by the case of Michael Combrune in chapter 2, could raise suspicions that what was on offer was dilettante conjecture, not valuable enough to withhold. Too much privacy, on the other hand, left clients with little means to judge the instructor's reputation – if, indeed, he even came to their attention in the first place. Though some instructors wrote personally to every significant brewer they could identify, it was far easier to promote their names by appearing in booksellers' lists and the monthly reviewing press.