Depending on what kind of grade you are talking about will dictate the best way to handle it with a diesel TV and fiver.
Unless it is just some rolling hills I won't use cruise control.
Always stay in tow/haul mode when towing.
If it is a moderate grade I will limit the max gear available. In my Ford 6-speed I can toggle down for example so that the transmission only has 3 or 4 gears to use, locking out 5th and 6th.
If it is a extremely steep grade I will use my transmission in strictly manual mode. What gear I lock in depends on speed and how steep of a grade.
The bottom line here is what others have said, and it is really not much different weather you are talking about electric brakes or air brakes. Let the engine/tranny keep your speed where you need it, not the brakes.
I am towing around 16,000 and have only experienced a couple really steep long grades out west that I had to use some brake. When I do I only get on them for 4 or 5 seconds to take a few MPH off and then stay off of them. If you ever experience total brake fade you won't want to have it happen twice.