I think I found a less painful way to farm a good chunk of twinkling titanite, well at least it beats farming stupid clams at Ash Lake and Crystal Caves. It involves farming crystal lizards, which is a pain in the ass, but there are about 10-12 farmable lizards in Crystal Hollow. These lizards will run if they see you a mile away so if you want to make it fast it requires the cat ring, so either trade in the skull lantern to hawk girl or go rank up the forest covenant.
Starting from the first bonfire at Great Hallow head to the right side of the ledge and drop to the large branch below. Head up the branch and you will notice after the branch turns that there is a small branch path and a ledge below that path leading into a cave. Drop to the small branch and gently tap to fall to the ledge below. Usually 2 to 3 of the crystal lizards will spawn in the cave/ the area it leads to and each one will drop 1 to 2 twinkling titanite each. Don't worry if you miss one or two, they'll keep respawning in that area. You can also check the next cave further along the original tree branch as one does respawn there too.
The spawn is random so if you don't see them in one run, just reset at the bonfire up top or use homeward bones. I managed to farm around 16 twinkling titanite using this method so hopefully it helps.
I am in my first playthrough, so it's not NG+ I assure you. For some reason Great Hallow randomizes its entire load of Crystal Lizards each time you use the bonfire. Meaning if you kill the ones in that cave and use the bonfire, they will eventually randomize into that cave again.