
WHEW!
My care paid off. I learned my lessons in FH5 (spent weeks looking for the last one).
I avoided Boards and breakables to stay on roads. If I got on a dirt road, I stayed on it until I hit highway. If a road had a forked entrance, I doubled back and took both. I rode every highway from beginning to end through Tokyo City. In the end I spent about 5 minutes looking for my last road - easy to spot.
And I know I got really lucky.