[oe] SDK / external toolchain

[George C. Huntington III]

Is there a guide to building an SDK then using it as an external
toolchain?  I'm not "getting it" when i read the /fine/ manual. 
also if I want to build and sdk for both x86_64 and x86_32 is that
possible, or is that 2 separate toolchains? 
how would I build an sdk for 32 bit from my 64 bit machine? ( i suspect
that it would involve canadian cross, but don't speak canadian so
step-by-step for dummies approach would be greatly appreciated!)