I assume the 'find the island' technique was a variation on the 'creeping line ahead'
No, Chichester set off for Norfolk Island en route New Zealand - Australia in a Fox (?) Moth with a hand held Marine sextant. He reckoned that if he tried to maintain the direct track he could end up somewhat North or South of the Island at ETA, and if he was way off, or in poor visibility, then he wouldn't be able to see it, so wouldn't know which way to turn.
He pre-computed the bearing of the sun that would pass through the island at ETA, then deliberately flew well North of the direct track, kept taking sun shots with his sextant until the bearing he had pre-computed came up, then he knew he was definitely North of track, so turned left and flew down the sun line bearing until he saw the island ahead. It worked.
I also know of a BOAC 707 Captain who flew across the Pole back to UK using two toothpicks stuck in two pieces of cheese, using a constant sun line - shadow of one across the other - and adjusting the heading every 20 minutes via an Astro sun line. A long story for another time !