That's the way I've always done it, but without the sugar. BTW, boiling the coffee is an art in itself as well.
I prefer to boil the water, throw in the coffee and lower the heat a bit (so it doesn't boil over) and let it continue to boil for a 2-3 minutes before running it through the sock. My ex MIL would heat milk up, then the coffee would go into that from the sock.
I gotta count mine- I bet I have a half dozen of new and used ones.