I have always operated on what some people call a "claytons" budjet, which is similar to what you are suggesting.
Meaning you get you pay, split it up between spending and investing, and just spend to spending side as you see fit. I have never had the patience or seen the need to break the spending right down to smalle items such as food, clothing, entertainment.
i just put 50% of my pay into my investing account and the other 50% gets spend where ever I feel like.