nwjohn,
I would have agreed with the others that a brush hog would be most valuable for clearing underbrush, but the fact that you also need to level the trails suggests that your intuition is right. I am doing the same kind of thing on my property and I own a scraper, brush hog and a tiller. It is my opinion that the scraper beats all of these for this task. Clearly, first, if possible, cut the vegetation down using a brush hog -- if you don't have one, use the scraper for two or three passes with the blades down. This will unroot grasses and weeds of diameter up to about 1/3 in.
The key to making a smooth path is to keep the trail clean of vegetation so that vegetation clumps don't develop.
Therefore, after scaping, use the FEL to take the dirt/vegetation combination to a separate pile. Let the vegetation rot for a year in the pile. Then use it as top soil somewhere else. If water along the trail is a problem, you might have to bring soil in from somewhere else. I have found that keeping a big pile of dirt for occasions such as these is very valuable and if you agree this may be a great place to start.
The problem I've had with my tiller in this application area is that the vegetation gets overly mixed up with the dirt requiring a greater proportion of dirt removal.
P.S. Is it "scraping" or "scapping"? I really don't know.
Buck