Doing musafaha (shaking hands) with both the hands as well as single hand is proved from holy Prophet Muhammad (صلى الله عليه وسلم). Doing musafaha with both the hands is mentioned in Bukhari which is more powerful and authentic. Hence it is better to do musafaha with both the hands.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband