It's good to be back
Glad to be back again. I was thinking about the Garuda and Naga background and remembered an anime called Macross Zero (don't know if you have seen it). Although it's not really south-east asian in flavor but i figured the background of the religion practiced in that anime could be useful for your Garuda-Naga relationship. Recalling as much as i can, i've come up with the following as a rough adaptation to your setting's background.
During ancient times there was only the Nagas and the Garudas. The Nagas lived in the sea while the Garudas borned with wings lived in the sky. One day, a Naga laughed at a Garuda saying : 'O mighty Garuda, borned of wings and rider of the sky. How pitiful that you shalt not know the life of the deep sea.'
The Garuda felt offended by the remark made by the Naga, swooped down on the Naga and tore it apart from the sky. From the blood of the Naga that fell upon the earth rose mankind who walked with feet and lived on the earth.
The Naga seeing that from their blood emerged a new race claim itself to be its master. They attacked the humans, seeking to subjugate them as their minion slaves and brought terror to the lives of humans. Humanity fearing the Naga pleaded to the Garuda for salvation. ' O mighty Garuda, borned of wings and tearer of the Naga. Deliver us from the Naga whom you have ripped to spill the blood from hence we came forth.'
The Garuda answered the pleas of the humans and once again from the heavenly skies, swooped down on the invading Nagas. A great battle ensued with Garudas shredding and Nagas bitting. The battle ended with the Naga being pushed back into their deep sea. Before the Garuda ascended back into the heavens, they gave the surviving humans a warning. For saving the humans from the Naga and having to lose members of their own race, the Garuda demand that their sacrifice be remembered. To do this the dead Garuda and Naga would become spirits in the earthly realm. They must appeace the spirits and not defile their sacred ground. Should man fail to do this, the Garuda would descend once more and destroy all of humanity.
Well, i guess it's still pretty lame at the moment
Maybe i'll come up with a better one but at least i think most of the gist is there.
Oh, and for the replacement of taint repellants. I know this is going to sound really odd (i was aiming for that direction anyway) but how about seashells ? Not good ?