To make it you need: 2 amplifiers, a guitar, 1/8th to 1/4th adapter, a shoe box, headphones*** and a microphone
***These need to be headphones you won't miss, I broke my pair of skullcandies because I turned the volume too high on my bass. Use cheap ones and don't turn the instrument up too loudly.
Step 1: Setting Up AMP1
And lay that microphone in the shoebox
Step 2: Setting Up AMP2
Plug a pair of headphones using a 1/8th to 1/4th adapter into amp2's output as shown
Lay the pair of headphones about an inch or two from the microphone in the box
Step 3: Cap It and Play
Make sure the volume on AMP2 is quiet to start off with and slowly raise it (if you raise it too much your headphones will break) it doesn't matter how loud you make AMP1
Strum away, it should be gritty. Play around with the spacing of the headphones.