I think one of the biggest factors in not having a dry brisket is to let it rest properly.
One hour rest at room temp under a loose foil tent seems
to make the juices hold up in the meat nicely. If your holding it foil
wrapped in a cooler for 2 or more hours just make sure it has cooled
off a bit before slicing. If its still steaming when you slice you can
actually watch the meat dry before your eyes.
I've never foiled a brisket while it was on the pit and only wrap if I need to hold it longer than 1 hour. I do baste or spray a few times during the cook
to keep the outside moist but I don't think that affects the inside much.
Never had much problem with dry brisket using the necked method, only
a few over the years, but every one is a little bit different and the odds are your going to run into one sometime.
Another way to do brisket w/o foil wrap is to use a foil pan (or make one out of foil) during part of the cook. Fernando up in Llano used to swear by
this method. I still do them this way occasionally.
Here's a link to an earlier thread that shows it....
http://www.myfreebulletinboard.com/...days=0&postorder=asc&highlight=texas&start=15