I find you don't need much for volume but plenty of distortion.
Here's an example with I think guitar rig or probably le pou (I can pull the session up but it's old and it doesn't really matter what sim), and then just moving around my monitors to find the nodes.
It's about 3 or 4 guitars and later I played around with some parameter modulation for the intro bit.
Don't waste your time with feedback plugins... they are weird.
http://soundcloud.com/roborules/gweegwoo