First of all I'd just say that you need to understand what the purpose of bump and rebound is -- shockwise. The hardness of the suspension comes from the springs and their rates ie. 300 lbs per inch etc or whatever is on your particular car. Adjustment of bump on the shock(spring being compressed)simply controls the speed at which the spring compresses NOT it's peceived hardness. Rebound ditto but in the opposite direction ie. spring going back to it's static length.
Settings wise , as a good starting point for testing on track to optimise --- I'd set FRONT bump to 1/4 and up to 1/3 rd of total clicks. REBOUND to 1/3 and up to 1/2 total clicks---OBVIOUSLY the lowest setting in each used together.
REAR bump 1/2 to 2/3rds of total clicks . REBOUND 2/3 and up to 3/4 qtrs of total clicks.
Rebound is useful for optimising the handling . If too much is used the result ' can be ' what we call jacking down --- that is to say that each time you throw the car into a corner the ' rebound ' will tend to not totally return the spring to it's full length then when you hit the next corner the car will have a shorter spring length to compress --- so gradually ' jacking ' the car lower over a lap. Hence me saying try the lower settings of each above ----------- you'll notice that the rear has more clicks , particularly on the rebound settings . This helps slow the diagonal transitional weight from inside rear wheel to outside front .
It's a time consuming thing arriving at a good set-up . Key thing is to only make one adjustment at a time then drive consistantly over the same piece of tarmac(track is best)for comparison with the previous setting. Tyre pressures need to be optimum for you car ie. handbook light load not fully loaded. For instance my 159 says 45 front 41 rear psi for very fast or fully loaded which I've tried but now set at 41 front 38 rear , even for fast driving.
Hope this helps a little.