my biggest tip for bringing them back, or at least getting power and volume is all in kareoke.
If you have a stereo system and some sort of vocal amplification and a microphone that's perfect.
I used to use my 500watt behringer PA connected to my computer.
make sure that your amplification makes you louder than the music, but the music is loud enough to be able to not hear you without amplification,
you also shouldnt turn the amplification up too high so that all you need to do is "whisper scream"
your goal is to build up adrenaline and force your self to be louder.
do it to music that really gets you pumped also.
warning however: do not overdo it, try not to strain out, or hurt your throat, use the right techniques and try to avoid your throat.
unfortunatly I use my throat to shape the gurgle in my vocals, which i fear has lead to the demise of my vocals.