Flawless Finish

Curious to know if anyone uses the flawlwss finish? A friend of mine uses it and has been trying to get me to, from what I read some use it a week before flipping to flower and others only at the end. Suppose to flush out the salt build up and he likes to start using it 2-3 weeks before harvest. I have smoked his stuff and it does have great taste and smell, but when I see his plants close to harvest I can't help but think he could have stacked on a lot more especially the last three weeks. Any thoughts?  Thanks.