Stamp duty by cash

Hi,
My Broker is asking to pay stamp duty in cash to advocate (which in my case would be 4.5 L),and registration by DD and states this is a usual process for agreement of sale for resale apartments. While on internet information allows differnet kind of payments - any inputs from senior members in the forum? He will be taking us to advocate office, and is okay if we spend a day in the process instead of letting advocate do the work.

Thanks.