after replacement i always clean the electrodes and shroud by blowing some clean, canned air over and through them to remove graphite dust formed during replacement.
After that i clean the graphite parts with clean acetone. Use a wooden cotton swap and clean the electrodes and shroud inside and out. Let them dry for a while.
BTW: don´t touch the graphite parts with bare hands. Use gloves. Try to avoid rubbing the tools too much against the graphite parts when replacing them.