As suggested, bedliner is an expense you'll never regret. I really prefer Line-X. Polishing the roof standing in the bed works for the rear of the cab, standing on the door frames sucks for doing the rest. Pick up one of the small scaffold-type stands... about 4 ft long x 2 ft high... at Lowes or HD. Makes a world of difference and it's also useful for the hood if you have a real high 4x4. Handy for SUV roofs as well.
As mentioned, the things seem HUGE unless you reduce the chore to smaller bites. Dealing with a personal vehicle at home at your leisure allows you to break up the job. Sometimes I'll just polish/wax one side and the front or rear then finish the other side the following weekend.
With that much sheetmetal real estate I found the blower off my Shop Vac to be handy to blow off water after washing allowing a real light job of drying. Keep a nice, slick LSP finish on it and you have very little water left to hand dry. Works so nice I now blow off any wash job instead of soaking WW towels. Gets the water out of creases, nooks and crannies as well.
TL