[NB: I believe the original reviewer may have made a mistake when indicating that the Gray trail is a gravel road. I rode both the Gray trail and the gravel road which is roughly parallel. The trail is clearly marked with "Grey" icons. So, I'm pretty confident on this point. Nonetheless, I extend my thanks and regards to the original reviewer for putting up multiple reviews, without which I would not have visited the area.]
The Gray trail is roughly parallel to the gravel road shown in one of the reviews. TH for NW end is at the edge of the road right near the end of the Red trail. TH for SE end is a junction with the White trail, which is not too far from where the White trail begins at the road. There are numerous drainage pipes under the trail which seem to really help avoid the deep, sticky mud that is common on some of the other trails. The course of the trail is gently rolling. There are some nice sections of open woodlands.