Cleanup is super easy, dissolves in warm water super quickly. A shower was plenty to get clean from covering my head and my place doesn't have a large hot water heater.
Just put the Marshmallows in a bowl and nuke them in the microwave for 30 to 60 seconds at a time and stir in between x of necessary. I think actually melting Marshmallows produces a way more fun product than the fluff stuff could hope to be!