Thanks! Using that approach I managed to get an ease out that I'm happy with.
In case anyone is interested my exact code was:
var rotationTween:TweenMax = TweenMax.to(_mainWheel, 5, {rotation: -degrees, ease: Quad.easeIn});
TweenLite.delayedCall(3.5, slowDown1);
TweenLite.delayedCall(5, slowDown2);
function slowDown1():void {
TweenLite.to(rotationTween, 4, {currentProgress: 1});
}
function slowDown2():void {
TweenLite.to(rotationTween, 5, {currentProgress: 1, ease: Quart.easeOut, onComplete: onWheelSpinComplete});
}