Some people call dehydrated burger "gravel" because it is so tough to rehydrate well. One way around this is to add 1/2 cup of bread crumbs per pound of burger, but then the hamburger tastes like bread crumbs though it is much easier to rehydrate.
My new method I just tried is to brown the hamburger just like alwaysw, then add a bunch of water--enough to cover it well. Then simmer it on the stove for a few hours. You could use a crock pot too if you have one. Don't worry about removing the grease...just pop the whole works in the fridge overnight, and peel the fat off the top after it hardens. You could probably boil it some more if you want to reduce the water, though when I did it, it was thick enough to spread unto dehydrator sheets just out of the pot. I tried rehydrating some this morning and was really pleased with the result. It was quite tender after only 15 minutes in hot water and it tasted good enough to use at home. Takes more time, but not really more work.
Anyway, thought I'd share. Good tripping this year!