you put wholes in the bottem of the pot or just let the water sit in the pot?
Water sitting in the pots is very, very very bad. It will cause root rot, and all sorts of problems.
I usually flush about one week prior to harvest, in MG I woulds agree that 2 weeks might be bettter. Just water with three times more water than the pot size you are using. EG. For a 5 Gallon pot flush with 15 gallons of water. If you really want to then you can also use a flushing addative like DNF Clear or any other decent brand.
If you don't flush the plant is still packed with nutes when you smoke it and it will a be harsh and not a good smoke. The flush is used to cause the plant to use up all of the nutes in the soil. It gives the plant a chance to flinish converting the nutes and causes the plant to make a final push and pump out as much resin as possible.