Wear coveralls, this stuff will stay on your skin for many days and eye protection.
I used dollar store brushes 3 inch and 1 inch for the smaller areas.
I painted the por15 then brushed on rust paint (armor coat- brand) as the top coat with separate brush.
Drive up on 4 wheel ramps and pressure wash underneath. It gets it sparkling clean. Start high and work your way down when painting.
Keep it ventilated as this stuff is not great to breathe in or wear a mask with filters. You can do the driveshaft with no issues either. I found the exhaust peeled after a year. I used a gallon of POR15 and a gallon of armor coat as a top coat. I painted all 4 calipers, frame, front drive shafts, UCA, LCA, tie rods, everything except for rotors, springs. I did as much of the undercarriage of the truck and box without removing the tank, etc. I did the rear axle, sway bars, and as much as I could reach. The more you remove, like the front bumper, the easier it will be.
If anything pops into my head I’ll update this.
Once your happy with it, use Krown rust proofing to keep it lasting forever.