How can a Muslim who smokes glorify God (tasbih), praise Him (hamd), and seek His forgiveness (istighfar) after finishing a cigarette, and is he required to wash his mouth before engaging in remembrance (dhikr) and prayer (salat)?

Smoking is forbidden (haram (definition)). As for removing its smell before Dhikr (remembrance of Allah) or prayer, its minimum ruling is that it is recommended (mustahabb), because the angels are bothered by offensive odors, such as those emanating from eating garlic and onions. The scholars have likened smoke to these. Therefore, it is recommended to wash the mouth and use a miswak before prayer or Dhikr, especially when the mouth's odor has changed.