Several books come to mind. You may not like how one author does it, but take a bit from one, another bit from another, and adapt to your particular style.
The second and third Asbell books have chapters that are specific to longbows, and how they differ from recurves. Byron Ferguson's Become the Arrow will give another perspective. Craig Ekin's book, Howard Hill, the Man and the Legend has a bit of Howard's shooting technique.
As stated, there is a wealth of information right here on TG. The Howard Hill thread is huge, but hidden in there are some good tips on shooting the longbow.