The best way is that if you can access the supply side of the fuel pump, break into the fuel line and use a rubber fuel line several feet long and attach one end to the suction of the fuel pump and put the other end into a gas can with two or three gallons of treated fuel. That way you won't need to treat nearly so much fuel to do the same thing.
Once you get it running from the fuel can, let it warm up for 15 minutes or so and then slowly increase the generator loading up to at leas 1/2 maximum or more. Let it then run loaded for an hour or two, unload it and let it idle for a few minuets to cool down, then shut down and reconnect the fuel line.
Good travelin! ........Kirk
Professional Volunteer
Fulltimer for 11 years, URL:www.adventure.1tree.net