Question: When  is it  sunnah to read Durood – before or after an action?

Answer: It is Mustahab to recite Durood before any action of importance.

ونص العلماء على استحبابها فى مواضع منها بين يدي سائر الأمور المهمة (در المحتار ج١ص٥١٨)

Translation-“The Ulama have clearly outlined that it is Mustahab to recite Durood at various instances, amongst them, before any action of importance.”