While the conventional wisdom is to fold with a spatula, several online resources suggest that folding with a whisk actually deflates less.
Epicurious prefers a balloon whisk to a spatula
That rubber spatula seems to take forever to incorporate flour into whites and the whole while, you watch as all the lovely volume you've whipped into your eggs slowly ...
The mechanism of a whisk is very different from a spatula. One is able to very gently fold the ingredients with a spatula while minimizing mixing. A whisk's tines will cause much more damage to the whipped mixture, deflating the fragile bubbles you worked so hard to create. It's really worth practicing with the correct tool. It won't take you long to master ...
Here's my recipe:
Take one cup of evaporated milk
Add one cup water
Pour down the drain
Seriously, evaporated milk will never taste like fresh milk, but there's a dietary need you can use it but will have to get used to the taste. A 1:1 ratio is probably a good starting place. If you have any cream or half-and-half you can add in that might ...
You can make something approximately 'milk-like' though it will taste more like that revolting UHT stuff they put in hotel rooms with the tea & coffee.
It will never go back to being 'fresh milk'.
Try it & see.