Depending on your rod, most suggest uplining one or two line sizes when using commercial shooting heads. Rio 30′ heads are already upsized two sizes for you and are my favorite.
As for casting them, it’s usually best not to wave them around too much. Get the head near the rod tip, back cast once then haul like heck on the forward cast and 100′ + isn’t out of the question.
The amount of overhang of the head past the rod tip should be experimented with for your rod and capability. Anywhere from right at the head to a few feet past the head is a good ballpark.