can't boot new kernel

This is a common question, maybe not suitable for this maillist, but I would
like to hear any ideas how to work it out.
Let suppose I build new world and kernel, reboot my current box, and new
kernel fails to boot (actually it hangs while detecting ata). So I should to
go into load prompt  and type 'boot /boot/kernel.bak/kernel', whouldn't I?
Ok, I try to boot and old kernel but now it fails too (maybe because of new
world?). So now I'm without any working kernel. The only way I see to solve
this trouble is to compile a sutable kernel on another machine, boot with
installation/recovery cd, escape to recovery shell, mount root partition and
replace /boot/kernel/ with another one? Or does load prompt can offer me any
builtin feature to avoid using recovery live cd (cuz i haven't neither such
cd, nor another bsd box actually :)
Thanks for responses.