It's much easier than that!

I visit the Library at the Manx Museum.
There I can look up the Burial Registers and the Monumental Inscriptions books.
Each entry in the MI books contains a grave reference - and most of the books have a map of the churchyard

Harrison burials, with an address of Truggan:
Alice Catherine, age 26, 26 April 1920
Elizabeth, 55, 3 July 1916
Henry, 47, 11 January 1905
Tom Hudson, 2 months, 3 April 1899