[Bunglespice]

So far I'm loving my Eleven Rack! I'm just having trouble figuring out one thing: How can I create intentional feedback?
You know how when you have a lot of pedals and you're too close to the cabinet it starts to feedback uncontrollably when you aren't playing? An example would be Nirvana - they have a lot of songs where in the break of the guitar playing, it is just leaking out noises everywhere? I love that raw sound and wanted to use it for a current project, but I'm not sure how to replicate that without an extra cabinet and too much gain.
I'm just lazy and don't feel like micing up a cabinet just for 20 seconds of feedback, especially since it won't fit the sound I'm getting from the 11R.
Any suggestions?