Missing Salah Due To Other Activities.
God has given the concession of combining and shorten the prayers, of Zuhar, Asr and Maghrib, Ishar. This concession does not require a real hardship, rather, it can be availed when one finds it difficult to perform a prayer on time. This concession is given for our worldly impediments.
Dust is not required. whatever is before you, just hit your hands on that and run your face and hands till elbows. The mention of dust or soil in the Quran is for a general use of a things which was readily available. The purpose is to keep the remembrance of Wudu somehow.