Line up to take a shot on goal.  As soon as you take the shot press
the 'R' key.  Keep the fire button pressed and when the screen
returns the players will be frozen and the ball will not be saved.

To get a free player:

Go to transfers and offer to buy a teams first striker and
substitute striker.  Now set the money equal to 0, and offer your
main striker, all in that order.  Assuming the other club accept the
bid, you will keep your main striker while acquiring the other teams
main striker also.  This should work for all players of the same
position.