Transformer potting

[bikerhifinut]

Has anyone here any experience of this?
I have a pair of large(ish)mains transformers that I'd like to pot up as a last ditch attempt at reducing the noise from the windings. Its not practical to suggest a rewind, I'd get a new pair made for the same or less. Neither is it worth any futile suggestions on impregnation as the offending winding is buried under layers of secondaries. I've had them examined by a transformer expert, whom I trust completely and his diagnosis was that the primary had not been wound tightly enough to the former and thus it was never going to be silent or quiet.
Now since I started running them at the correct 230V by dint of a homebrew autotransformer/bucking arrangement they do run quite cool and so I should be ok to use a thermally conductive potting compound.
So I need a container to pot them in and some compound.
Any help or suggestions? I'm no good at metal fabrication so please no "buy a sheet of metal and bend it" stuff unless you know of a good inexpensive workshop who could make me one. I was advised by someone that an ABS type box could work but my feeling is a thermally conductive substance eg metal would be better.
This is a last ditch attempt at silencing what would otherwise be scrap as a mechanically noisy mains transformer has no place in a hi fi amplifier.

Andy.