In a mixer bowl, combine meringue powder and ⅓ cup water. Mix for a few minutes. Add powdered sugar, glycerin, corn syrup, and vanilla, then mix. With mixer on, slowly add remaining ⅓ cup of water. If the icing is still too thick, add drops of water until it resembles the consistency of creamy peanut butter. Beat it for 5 to 7 minutes. Melvin puts a bead of water in the bottom of a Tupperware bowl before adding icing, covers bowl, and stores it for a few days on the counter.