First time I've ever done that. The truck isn't one of those vehicles I typically mess around with. It's easy to screw up the brakes flushing them, and given how difficult it is to stop once it's moving I leave it alone.
Couldn't do that with my upcoming trip across the pass.
So I changed the pads, , discovered that my left-front was hanging up and not even engaging, replaced all the springs, guides, boots, and then flushed the fluid.
What a huge difference that made, old stuff was a deep dark green, bleeders were all rusted, left front rotor is warped (slightly). I flushed it using one of those MityVac multi-purpose bleeders - no help needed, no pumping the brakes, just crack open the bleeder, fill up the reservoir with gunk, repeat as needed.
Now I don't have to worry about my brakes failing hauling that bike across the pass. I really wish I hadn't waited as long as I did given how easy it was.