Thrasher02, I recorded a quick sample of the technique I use for sludge metal. First, use a reverb with a huge room size (you can choose presets on most computers for this, and they have it on Fruityloops). I use my mixer set to "cathedral" and it gives me a very long reverb sound with tonnes of echo. I apply this to both guitar and mic. Ride the side of your pic up and down the strings while breathing in (making a high pitch sound). Sounds amazing.
Here's the sample
Enjoy!