There will be 2 lines under the hoop. in one line the person at the front will start with the ball and the other line the person whos second will start with the ball.
The person at the front of the line without the ball will run around the the key and receive the ball from the front person in the other line when he gets to the low post block.
If the players are making the shots consistantly then get them to shoot from further out.
Rebounding is the least glamorous thing in basketball and one of the most decisive. It is also almost entirely a habit, which means it is entirely coachable.
Good spacing is only the start. The best modern offences teach players to attack the defence's rotations and play in a permanent 4-on-3 - here is how to coach that read.
The ball screen produces almost half of all professional offensive possessions, yet most teams still teach it as a memorised play. The modern approach trains the read - giving players a framework to decide based on what the defence does, not what the coach called.