I have cleaned mine many times with alcohol hand cleaner. It has managed to get so full of gunk as to stop spinning entirely and yes lots of flare and burning at the cut happens.
By putting one end of a C-Pap hose in a shop vac the rubbery end is small and flexible enough to jam into the chute that the air comes out of and pull lots of air through even with the Glowforge shut down.
Under these conditions the fan will only spin when it is freed up and I dump quite a bit of the cleaner into the fan intake . the cleaner dissolves the gunk and the vacuum sucks out everything so there is nothing particle or liquid that does not make it .
When the fan is free it will spin up and I leave it doing so for a half hour drying out and staying freed up for some time after but it still needs frequent attention as now that I am aware of the need I have much less tolerance for the flaring, though it never totally ceases.