There is no real need to flush and flushing unnecessarily can do more harm than good.
You can continue LST all the way through until there are little "budlets".
Once there are little "budlets" and they have "decided" on where they are going to grow, direction wise, stop with the LST, as once the "budlets" get set to a direction, they don't like being messed around with needlessly.
Hope this helps,..........
Organoman.