I've tried every method (including smoking, and I quickly found low temp smoking poultry rarely turns out well.. it's gotta be done at least 325)... and here's what I do now.. and it's simple.
Rub bird with lawry's and cracked pepper.. put in cooking bag, throw in onions carrots and celery, cook breast side down 15min/lb until the last hour... last hour take out the juice for gravy, flip to breast side up (if the bird stays in one piece that is!)
This year we did a 25lb bird. When I went to flip it it literally fell apart. So the flip didn't work, but the turkey turned out PHENOMENAL and the gravy was the best. Instead of the l flip I ended up pulling the bones, putting the meat back in a roaster pan (white on bottom, dark on top with some skin) and left it at 200 until everything else was ready.
Was a raving success. Except for presentation lol... but every time I've taken a bird out that looks good, the white meat is dry as a bone.