Was up there a few days ago...walk up the trail to North Brother, keep going straight past the summit sign for a few feet, then look to your left for cairns that mark a safe way to walk down through the fragile North Brother alpine zone. The path winds around a little bit out of the way before it dips into the trees.
From there, my best advice would be to look down at the footbed - it's a pretty obvious herd path to follow if you look at your feet. Someone put up navigational aides awhile back, but I suspect they may be gone by the end of the holiday weekend.
Pants and a long sleeve shirt are a good idea - even though the footbed is well beat out, there are plenty of branches, etc.