Try this, one guitar amp, one of this:
and this:
Set the depth and res of the flanger really high, max; and the rate about medium to medium high, the manual low. For the distortion, just make it really distorted and put the volume at low(you can use the guitar amp volume to make it louder)The other settings are equalizer setings, set according to tone preference. Then play your guitar, anyway you want and while it's sustaining feedback, twiddle with the res knob...