The green stuff was bad gas. It's what happens when gas stays in contact with brass for too long.
As for the flooding...your float got stuck. Give the carb a couple quick smacks with the handle of a screwdriver or with a rubber mallet to try to unstick the float.
Seeing as you had bad gas (essentially turpentine), it would be a good idea to remove the carb and float bowl (NOTHING ELSE) and spray everything out really good with some carb cleaner.