I got lucky on a Briggs motor on a Genset that sat over the winter one time. I pulled it out in the Spring to change the oil, and unscrewed the oil fill plug to be greeted by a pent-up deluge of gas/oil mix pouring out of the crankcase like a garden hose!
Drained the fuel tank and then tipped the generator on each side to get out every drop. Then I put fresh oil in, and tipped the generator on its sides again to try and force oil up on the cylinder walls.
Pulled the spark plug and slowly pulling the starter rope about 20 times really slow to get the piston moving. Put some gas in it and fired it up. It got an in-line fuel shut off mechanism after that.
Still have that generator 8 years or so later use it occasionally. But I still check the oil level first after it has set for a while.