I read one suggestion on the forum to run a guitar string into one of the small air passage hole on the air intake side of the carburetor and into the "emulsion tube"? Not quite sure about the emulsion tube.
The emulsion tubes resides near the outlet of a jet orifice. It's a tube with cross-drilled holes, liquid flows into the tube and then air is mixed with it, forming a fuel/air emulsion that is later delivered to the carb throat. Both the idle jet and the main jet have these emulsion tubes. An air/fuel emulsion flows, and more readily mixes, with the flow of air in the carb throat.
Should the guitar string be used to run into the slow/idle small air intake hole also for cleaning purposes.
As a last resort, if you can't clear the orifice with less aggressive means. Guitar string/hard, jet body/soft, risk of orifice alteration.
I have also seen a couple of members mention Simple Green as a good cleaner. Is this for cleaning the outside of the carburetor or is it for soaking the entire carb to clean the inside?
From reports, it is used over the entire carb inside and out. Not over night, as the metal will discolor due to pH issues.
I prefer carb cleaner. Those aerosol cans with the little red tube taped on to it is pretty handy for "normal" cleaning. Carb dip for the worst ones. Both these eat rubber bits, whereas the simple green won't. Each tool has it use and required knowledge base. The pressure of the aerosol is great for proving air a fuel passageways. Better than compressed air. Seeing air movement can be problematic.