Water Resistant cone dope Scan 18W

Guys, hoping you can help, I'm looking for some dope make some SS Rev's more moisture restistant. I am not worried about adding a little mass, they actually model a little better for my application, but I have no idea if they need to be made stiffer or softer.

Unit: 18W/4531G00
Enclosure: Sealed 3L
Freq Response req: 50-800hz

I have a very interesting long thread which many of you contributed too which suggested Dammar amoungst other prduct, but the emphasis was not so much on water-proofing per say.

Is Dammar waterproof? And I see it's available in spray form, would this be easier to apply?

Thanks for any advice you may have :)