Off the top of my head, if in doubt, whisk the whites separately (to break apart their globbiness, doesn’t work properly with the yolk included), stir some starch in a bit of soy sauce and that into the yolk and then stir in the unglobbed whites, should give a quite uniform erm batter. I think technically it’s a batter.
Basically, how Chinese Cooking Demystified (on youtube) taught me to get perfect, juicy, fluffy, scrambled eggs every single time without fail, the additional water acts as a raising agent (steam) and gets bound up in the starch instead of escaping. Behaves very well in a pan so I bet it works well in a waffle iron. The soy sauce is of course optional taste-wise but the water in it is mandatory, you need some salt anyway and while you’re at it yeah why not soy.