The leader can use the Right Turn to switch the hands from Parallel Hold to Handshake, Crosshold or Reverse Crosshold. There are two different ways to do this. Both options assume that the right hand of the leader is not holding the followers hand.
The first option is to do a normal Right Turn for the follower. On 3, the leader left hand should be up to indicate the turn. On count 2 to 3, the leader can raise both the left and right hand. Then the leader can overtake the followers hand with the right hand. Make sure this is done before the follower turns on 5.
The second option is to do a Right Turn as the leader. Instead of raising the hand above the head to turn underneath it, keep the left hand low. While making the turn, on 2, the leader can switch holding the followers hand from left to right. The hand position will not be natural immediately (the leader holds the followers hand a bit to the side), so the leader has to adjust the hand position by for example scooping the followers hand.