I had a New Rookie a few years ago and I fitted the belly airbrake and also used the foreplanes as an airbrake.

The belly airbrake is adequate with idle throttle on my P-80. One tip though, bolt the control horn right through. Don't just glue it to the inner skin as in the instructions. Mine broke free by pulling a piece of inner skin away from the thin foam material in the middle of the laminate.

The canard airbrake is adequate on its own too, with idle throttle. No problems using it at all. It is not gradual however, it is on or off.

Both actingtogether is great. It gives very positive descent and allows a little throttle to be used which makes go-arounds easier. Just firewall the throttle, close the airbrake, flip the foreplane back to normal, retract the gear and ups she goes.

Foran approach on idle throttlewithout any airbrake you need to take her a long long way downwind, come in really low and flat and expect a long float.
With both brakes operating, obstacle clearance on the approach is no longer a problem.