Just pop your keys off, they lever off, but be warned what you find is seldom pretty ( and do it one at a time or you'll be trying to decide which goes where like me;)
Yeah! I do a lot of blowing, turn it up and give it a few good taps.
Otherwise buy a new one. Bought a new one a month ago £8.50 in 'Comet' now that wont break the bank will it? (Beautiful clear bright white letters too.)