Are we talking about silica wicks, I assume?
Just do a simple dry burn -remove the
tank, with the wicks exposed wash them, then pulse your firing button, letting the
coils glow for only little bits of time, until all of the residue is burned off, then wash again. Silica can withstand the heat, and you'll have clean wicks in no time.
Youtube: "how to dryburn X", where 'x' is your atomiser/
tank/what-have-you