Take the choke out of the gun. Put the string of your bore snake through the choke and tie the string to a door knob or something. Grab the other end of the snake and stretch it out tight. While holding the snake tight with one hand, scrub the choke back and forth across the brushes. You can make many times the number of passes through the choke this way than you can with a brush on a rod and there is no rod to possibly damage the lip of the choke.