When you deposit/withdraw BTS from an exchange it all comes from a hot wallet?
So say you have 'X' BTS couldn't you...
Give person A 'X' BTS votes.
Send 'X' BTS to BTC38.
Withdraw 'X' BTS from BTC38. (But it would mostly be different BTS if it came from their hot wallet pool.)
Carry on repeating process until their whole hot wallet is voting for your delegate.