Not as good as a course, but a great place to start is a copy of "Dutton's Navigation and Piloting" published by the Naval Institute. Its got 12 chapters covering Celestial Navigation, starting with Chapter 18, "Navigational Astronomy" and ending with Chapter 29 " The Practice of Celestial Navigation"
It was a basic text and reference book for our full blown Celestial Navigation class at USNA back in the early 80s...
Earlier edition was the text at USNA back in the late 60's. Great book.
Like a normal lead, you'l want to adjust it fore and aft. Different reach angles will call for different leads for the barber haul. Eg, almost beating, it'll be further aft than almost being able to set a chute.
Keep looking at the leach of the sail as well as the top third.