Before Carl Demerow, the AMC Trail Crew was led by Bob Proudman (now Director of the ATC in Harpers Ferry) and then Reuben Rajala, who also wrote excellent trail maintenance guides, which can be found used at:
http://dogbert.abebooks.com/servlet/SearchResults?sts=t&an=Robert+Proudman&y=10&x=36
I wish that trail maintenance organizations and volunteers paid more attention to clipping, especially to benefit those who like to hike in rain and the winter. The term "trail standardizing," which is an important chapter in Proudman's books, refers to clipping back the brush such that a 4 ft by 8 ft sheet of plywood tied onto an AMC packboard can be carried on the trail without obstruction (i.e., cut the branches back close to the trunk and as high as one can reach, and if necessary remove the encroaching saplings altogether at the base of their trunks). Besides allowing passage without one getting drenched by wet branches, scalp wounds, and poked out eyeballs, clipped trails also dry out more quickly as the sun can better reach the muddy sections. Clean water bars are important, but so is a well clipped trail, IMHO.
