basically what flushing is, is watering the plant until the water that comes out the bottom is much more clear .. at first it'll be yellowish in colour...it may take 2 or 3 regular waterings (done in a short period) to get the water coming out of the pot more clear.

this is basically replacing the stale water in the soil... YES you can drown the roots.. but that's only if it's sitting in the water...the soil only absorbs so much.. hence need to do this a couple times.

GL!