It's wash time
Your bucket is ¾ full (not you, the bucket!). You have used the correct dosage of shampoo, by using just one capful, adding it to the bucket when the water level is half full, as if you add the wash solution too early, you will get a huge head of suds and very little water! Your aim is to get a nice layer of suds, about 10cm worth, so they sit just above the rim of your bucket. Rinse the lid clean in the wash water as well, so you can be sure to get the full dose.
You have thoroughly drenched the car, making sure to have rinsed away as much of the dirt and "heavier" elements off from the car, especially down on the lower areas with a slightly stronger water pressure.