breading/crumbing: mixing the eggs and flour?
In general, when battering, wet sticks to dry and dry sticks to wet, but they don't stick to themselves.

Thus, if starting with wet food, like meat, the process is usually:


flour (dry, sticks to the meat, which is wet)
eggs (wet, sticks to the flour, which is dry)
crumbs (dry, sticks to the eggs, which are wet)


If you have a wet layer right next to wet food, the batter will fall off during cooking.  If you try to stick dry to dry or wet to wet, it just won't adhere well.

You don't need the whole process (you could just use flour and omit the other two layers, for example), but the wet-dry rule is important.

It would be possible to mix (e.g.) eggs and flour to make a wet batter, but that should still be applied to food which is dry.  If the food isn't dry, it would need to be floured.