As you have learned, reversing the prop does not reverse the direction of the thrust. I'm not sure what type of electric motor that you have. there are two technologies. A DC brushed motor has two wires connecting the speed control to the motor. To reverse the direction of rotation on this type of motor, you must switch the two wires. The other (more expensive) type of electric motor is an AC brushless motor. these motors can be identified by THREE wires running between the speed controller and the motor. to reverse the direction you swap any two of the wires.
Make sure your prop rotates such that the leading edge of the prop goes first. typically, this means the numbers on the prop (such as "6x5") face forward.