If you use a computer the process is much faster, though it still takes a degree of diligence to keep it accurate. The idea is to know precisely how much of any product you have on the shelf, at all times. By proper auditing of the perpetual inventory system you should be able to at least reduce the outright theft of product from the shelves. Several methods are employed to reduce the potential for waste or theft by bartenders during the function. One system uses a cup count system, where the actual cups used are counted against the cash turned in.
Some operations use both a cup count and physical inventories to hold bartenders accountable.
In order to manage your pour cost on liquor, most firms require their bartenders to measure out each cocktail with a jigger. Traditional pours are one and a quarter ounces for a regular cocktail and two ounces for a martini or manhattan. Even with a jigger, your bartenders have a vested interest in over-pouring, and will tend to trail the pour in order to get a few extra drops into the drink. Your best shot at controlling over-pouring is to maintain a visible management presence in the room. There is nothing wrong with stepping in behind a bartender from time to time to give them a hand, or even to take over to give them a quick break.