You don't need to increase humidity for that long really - wait until he returns to normal colouration after being in blue and it should only be a couple of days or so.

You could try putting him in a tied wet pillowcase overnight in his enclosure to see if his attempts to escape manage to loosen the head area a bit.

If you post your setup we might be able to suggest ways of increasing the humidity without causing problems - like the damp hide mentioned above.