> If you've waded through all that, now you get the inevitable
> A. What is the "Eachtrach Cholm Cille" and where can I read it?
This is just a wild stab in the dark, but maybe what is meant here is
the benefit of reciting the Amra Choilm Chille?
> B. How do you "put" a lay into bread or butter?
It is not untypical for charms to be sung into butter - which thus is
turned into a magical salve and then smeared upon a wound etc. E.g. a
charm against "sirem" (prob. scabies; from 24 B 3, p. 27; nr. I in
Carney, "A Collection of Irish Charms", Saga och Sed 1960, 144 ff.):
Obaid ar sirem. "Slan cru, marb in tru bis a ceand. N." Slan do ceand
ar sin. A gabail fo .7. 7 paidir roimpe 7 na diaig. a nem [leg.: an
im] con a blathaig 7 a cumelt de. foirid sirem 7 milai crina 7 lomus
7 is menic ro dearbad.
A charm against "sirem". "Whole is/be blood, dead is/be the wretch
that is in N's head". Your head is healed by that. Say it seven times
with a pater before and after it, in butter with the buttermilk from
it and rub it on it. It helps with "sirem" and crab-lice (?) and
baldness, and it has often been proved.