Whatever you do, don't try to wipe them clean or poke anything in them, they are very delicate.
Look for special solvent cartridges, you probably only need one because you can swap it from one position to the next as you unblock each color. If you can't find an exact solvent cartridge, keep one of you old empty ones and buy a bottle of solvent from an ink supplier. With care you can inject solvent into the old casing and use that as the cleaning cartidge.
Brian.