Head North at HWY 19 and make sure you turn back before you are at half a tank. That is a bout it.
the Bethy Creek cut isn't too easy to navigate. If you want to go to Bethy and check it out, I would go by land, put in there and ask Randall for directions out of the lake. It is a little tricky and hidden from the river.
The Trinity is really one of the most amazing places in the world to ride.