Grip the nib and feed together with your thumb and finger, pull out from the nib unit. If it is stuck with dried ink, give the unit a soak in warm plain tap water. A slight wiggle of the nib and feed will bring it clear. Do not use force.

Clean the feed in warm water, use a soft toothbrush if needed. You can also leave it to soak overnight. No need for detergent or cleaning sovents of any kind.