Flushing?

I know when using soil you use only pH'd water between most feedings, and the last 2-3 weeks, maybe a little molasses. But what about if you're using 1 gal pots you pour 2 gal of water into it, how often do you do that and when? Which one is actually called flushing, and what is the other one called?

its basically 3times the pot capacity in water,,,then just give straight water after that or mollasses water,,,,,,,,,,,,peace

Thanks for the quick response! I think I got it now. 3 gal of water the day they stop getting nutes. I guess both are part of the whole flushing process.