Updated quest: http://l.j-factor.com/zeldaclassic/NeoFirst_L.qst (Remove the underscore from the filename if you can't load it)
Updated scripts: http://l.j-factor.com/zeldaclassic/NeoFirst.txt
What I've done recently is code up two scripted items.
When you start the quest, notice that the A button is assigned to the Magical Water. Apply it to the objects in the room.
Now, exit the dungeon. You have an Empty Bottle in slot B. Walk onto the dock and scoop up some water.
The Magical Water scripted item uses no FFCs, so it can be used in any screen without hesitation. The splash of water is a Non-gameplay Item (which has a 'Hearts Required' of 255) which is used (and later removed) by the quest's global script to produce the appropriate results.
However! Since the Magical Water can quench torches, a problem of internal consistency emerges. In the case of wall-mounted torches that are flush with the dungeon floor, it is expected (and may at some point be desired) that watering them will also eliminate their flame. So, for all of those kinds of combos, an equal amount of unlit versions may need to be added.
(As for layer 1 torches... let's just keep them above the floor. And as for those braziers in ST's Forest Temple... their flame is visually distinct enough that we can get away with considering them an 'oil fire'.)
Also: using water to remove Zol Fire is currently a post-2.5 technology.
Also also: No, dumping water on stumps isn't going to make the bushes grow again. The water isn't that magical.
Furthermore: If you use cheats to warp to DMap 2 screen 2, you get to see my first scripted Shop. The script used there is my own.
