RE: how long to rattle and grunt
My general rule of thumb is;
Pre rut, tickle a little but not much. finish with a little grunt. Do this in a cycle of tickle about 20 to 30 sec. and do about every hour.
During rut. Rattle hard for about 30 sec. to about 1 min. Do every hour. Finish with a quick grunt followed by a little longer grunt. You can even stomp the ground and rake the trees around during the rut.
Spot rattleing. During the rut, when I see a buck I want to bring in, I give him a little grunt first, After words I rattle, not as hard as I do blindly, then wait. Dont give up if he disapears, He might not feel comfortable turning back, but might hit cover then turn back taking a different path.
One thing you must consider when rattling is where you are at. Set up where you are at a cross wind of their path. Big bucks will never come to a fight with the wind to their back. Dont over do it, it takes some bucks 30 min to an hour to respond. If you rattle too often you will spook the big guys.
Hope some of this works for you. Good luck.