Cob: weather sealer for cob bench

[John Fordice]

Dear Cobbers,
I did a couple of cob benches with a bunch of school kids last spring. 
They're well dried now & I think it's best if they are sealed for rain
protection before the wet season starts.  I've heard that a mix of
linseed oil & bees wax will work, but don't know the first thing about
it. Can anybody illucidate ?

Also will appreciate any other methods folks may know of.

The benches are finished with a mud plaster that has about 1/3 horse
shit mixed in.  It made great plaster, but I suspect that an additional
sealer will assure longevity of the weather surfaces.

Any advice will be appreciated.

john fordice
Maker of Cobbers Thumbs
TCCP