Pre marking the tail does not give new recruits a chance to learn the art. In the long run you will get less and less volunteers.
Without trail school, we should use every new trail cut as an oppertunity share and teach the hows and whys.
Pre-marking the trail is so that we aren't wasting the time of our volunteers. It's not very time effective for anybody if we get 10-20 volunteers on the trail, and then spend the next hour scouting/marking/flagging the trail work to be done. There is no way that many volunteers can effectively learn anything learn anything when the class size is that large, and when the focus is getting the trail marked so that work can get started, not education.
There is discussion currently about a couple of IMBA chapters working together to get a Trail School started again.
But, if someone wants to learn the art of scouting and marking trail, I would suggest reaching out to one of the Trail Coordinators, or the chapter, and express your interest. Many of the TCs got their start by working with other TCs on the pre-work done before the trail days, scouting and marking. There is more time for effective teaching in these situations, and the TCs are always open for other thoughts and suggestions, and if need be, explain why those suggestions are good or not, and why they may or may not work.