Personally I thoroughly mix in about a cup (for a 6 gallon batch) of corn sugar into the bottling bucket. Your method of adding 4 grams per bottle would be effective, but also time consuming.
Found this info below on another page. Might be helpful.
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Measuring priming sugar
The most accurate method of measuring priming sugar is by weight but for bottle priming the most convenient method is by volume using a measuring spoon. Much confusion arises here because the same spoon holds different weights of different sugars.
Measurements show that a standard (5 ml; 1/6 fl oz) kitchen teaspoon holds 4.5 g (1/6 oz) of sucrose but only 3.4 g (1/8 oz) of dextrose or glucose powder. This difference is sufficient to explain the changes homebrewers report when switching from one priming sugar to another, particularly as many kit recipes suggest rather high priming rates to produce a beer ready for drinking soon after bottling; these beers often become over-carbonated after a few weeks/months.
Another useful 'spoon' is a homebrew bottling measure, which holds 6 g (1/5 oz) of sucrose (4.5 g; 1/6 oz dextrose) on one side and 3 g (2.3g dextrose) on the other. Thus, either a standard teaspoon of sucrose (4.5 g; 1/6 oz) or a generous bottling measure of dextrose (5.2 g; 1/5 oz) per 750 ml (26 fl oz) bottle will give the same final level of carbonation (+1.5 vol. CO2). But if the sugars were reversed (teaspoon of dextrose or bottling measure of sucrose), the final beer would be under- or over-carbonated by 0.4 vol. CO2.
For really reliable results, you need to know exactly how much priming sugar your measuring spoon holds. If you have accurate scales, you can check directly. However, it's best to average by adding, say, 20 scoops to a small container and weighing them all at once. If your scales aren't accurate enough, you could ask your homebrew shop to do the weighing. Or buy some good scales - they're also useful for weighing hops and letters!
For comparison with the priming rate suggested above, it is useful to note that the 3/4 cup corn sugar (4 oz. dry weight) per 5 US gallons called for in many American recipes is equivalent to a priming rate of 6 g/l.
