If I have really recalcitrant ink in there, I use my Flushing Syringe of Doom which is a normal syringe glued to a cartridge with a hole in the end of it. This can plug directly in where the cartridge would go, and you can thus use it to very thoroughly flush out any crud or old ink in the comb or elsewhere on the writing end.

At present I have an International Short cartridge stuck on the end, which hooks up pretty well even to pens that don't take that type, at least just long enough to blast them out.

For pen bodies and other parts, invest in a cheap ultrasonic cleaner. Just filling it with water is fine. It will vibrate out dried ink from anything that can be submerged and make it ready for rinsing.