Modge Podge is a craft glue most commonly used to seal and finish decoupage art but can be used in any paper-based craft including papier mache.
To make a jar of fake / homemade Modge Podge you need:
1 cup of glue (any white glue such as wood glue / cold glue works) 1/3 cup of water.
Pour into a jar with lid. Mix well by tightly closing the lid and shaking the contents. Use with a brush or sponge. These proportions are perfect – too much water will make it too runny and will not stick properly.