Some sort of in-game timer starts when you first start the game from the 3ds menu which affects gibdo ba. About 2:10 after the game starts up you get to a good place where the wrong warp will work.
Save at mountain village in spring
Close the game
Reopen, start a timer if necessary
Go to the hot spring grotto at twin islands
Dupe over gibdo
At about 2:10 after starting the game (or about 1 in game hour of inverted time, assuming you did not lose a significant amount of time for anything where time does not pass) catch hotspring water in gibdo bottle
As soon as you clear the text, mash ocarina and play inverted song of time or the moon will crash
Dump the hotspring water and catch it again, this should cause time to go crazy
Exit the grotto and after the day change you should be in gyorgs room
Mash ocarina when the gyorg fight starts and play inverted sot or the moon will crash very quickly (if you want to be safe you can play isot after the 2nd hsw catch while still in the grotto and exit, but you'll have to play sodt and wait until the next real day transition)
I'm not sure exactly how lenient the timing for catching hsw is but the different patterns I was getting seem to have changed in intervals of ~10-20 seconds so it shouldnt be too precise. This can probably be improved a lot but its a starting point.