The method I use to clean the windways of my calliope whistles is
simple.  I use a set of feeler gauges I bought at an auto parts store.

The set is a series of flat steel blades from 0.001" thickness, in
0.001" increments up to whatever.  I think there are about twenty or
more of them in the set I have.  They swing out from a pivot on one end
so there is no chance of losing a single one.

I've had them for thirty or more years so I don't know what they'd cost
now but they are well worthwhile to have and they work very well to
clean out the residue in the calliope whistles.

Hal Davis