My last grow was in soil. Fox Farms Ocean Forest. I'm a new grower, grain of salt etc.
I started to leech with a tsp of Florakleen/gallon when the trichomes were 75% milky.
I would give them enough for a large runnof, like 30% the first few times with florakleen.
After that I just gave them water until the trichomes were about 5 percent amber on the tops. just my preference.
The goal for me is to harvest when they are all milky at least.
I don't really want much amber. The cannabanoids will continue to break down during cure and storage and I like to see the whole gamut of effects as they age.
This is a personal preference, it is more common for people to harvest with more amber.
Anyway I hope that helps to some degree.