Budget Horn Deadening

[Audio_by_Goodwill]

Pykrete;
Pykrete - Wikipedia, the free encyclopedia
Non toxic torpedo proof water and wood pulp ice polymer.

Mythbusters did an episode on pykrete........ it was very interesting!

Trex wood-polymer decking;
http://www.trex.com/
Non toxic wood pulp and plasic polymer.

That would make an interesting material to cast the whole horn.

Cheap non toxic horn deadening. Acrylic Latex plus wood pulp polymer sound deadener; take wife's mixing bowl and mixer, add roof coating and lots of saw dust(the courser the better), mix thoroughly with as much filler as can be suspended in latex to prevent shrinkage, dip horn into or pour in external cavities. $19/gallon.

Are you suggesting the paint and the roof coating, or choosing one or the other?
I think you'd run into problems pouring it. Paint isn't designed to go on thick....... the roof stuff might handle a bit more thickness. I beleive even the sand/paint trick has to be layered.