For my old two stroke, I did a two step process. I would pull the plugs and spray it directly into the cylinders. Let it soak overnight. When I cranked it up, it looked like a house fire with all the smoke. I pulled the breather off the carbs and would spray it directly into each carb while it was running. Just enough to keep it running and not choke out and die. More smoke!
Only had to do it once a year. I used that motor from 1977 until 2008 and never had a problem with it. Probably only changed the plugs twice the entire time that I had it.