[Naagzh]

I believe in the Deftones stuff there's a filter of some kind on the vocals. You might try Izotope Vinyl or a telephone-voice type of effect. Or try Amplitube or other distortion plug.

Compression on vocals should be used to even out the quiet and loud parts. You shouldn't "hear" the compressor working, unless you're going for a specific colour or pumping sound.