When using flurry of blows, a monk may attack only with unarmed strikes or with special monk weapons (kama, nunchaku, quarterstaff, sai, shuriken, and siangham). She may attack with unarmed strikes and special monk weapons interchangeably as desired. When using weapons as part of a flurry of blows, a monk applies her Strength bonus (not Str bonus x ƒn1-1/2 or xƒn1/2) to her damage rolls for all successful attacks, whether she wields a weapon in one or both hands. The monk can¡¦t use any weapon other than a special monk weapon as part of a flurry of blows.
In the case of the quarterstaff, each end counts as a separate weapon for the purpose of using the flurry of blows ability. Even though the quarterstaff requires two hands to use, a monk may still intersperse unarmed strikes with quarterstaff strikes, assuming that she has enough attacks in her flurry of blows routine to do so.