I love Deakins articles but most of what you read in them can only be applied in an AC with good engine instrumentation and with a fuel injected engine...
To the question of time... turning the knob is just pointless accuracy for this way of leaning, pull slowly, I do not really know how slowly I do it but it definitely takes less than 10 seconds, maybe under 5 from full rich until I get at rough engine and in the Cessna I fly its just a 1cm push from that to have a great running engine that uses several liters less per hour than running full rich.