well, be sure to use a 1/4inch SCREEN on all the stuff between bottles, and other stuff, the smaller stuff is much better, you know - coins, rings, pocket watches, buttons, you name it!
Metal detect, for sure - at each level, down to undisturbed soil, bedrock, whatever! Long probes may help find outhouse pits, but shorter ones get to loose, un-consolideated spots, good stuff, right away, then go from there! And be sure to use sturdy boots (nails!) and gloves (glass!),
Also, don't expect to find the outhouse locations, too far away from the house/cabin, depends tho, so another variable was water sources, prevailing winds, other things that you would use if you located one for yourself....
Good luck, Happy Hunting!