transpose from "treble" to "bass"

[Andreas Gemperle]

Hi

I have a piece written for "barition in b" (\key c \major | "clef: treble").
I'd like to transpose it for a "trombone in c". ("clef: bass")

Theoretical: C major becomes B major (2b) and a "g" becomes" a "f".  And clef 
has to become bass
How can I do this automaticly with lilypond?

I have looked for this in the documentation, but I couldn't find a  sufficient 
solution (for me). I know there is a transpose-command, but I don't know how 
to use it for changing the key and clef at the same time. I tried it, but it 
didn't work :(
Is there a good example??

My version: GNU LilyPond 2.4.5
System: Linux/Debian

Thank you

Lg
Andi