3ds Max Animation :: Revealing Models With Masks

I've been following one of Louis Marcoux's tutorials on youtube where he animates a gradient map inside a material in the cut out or opacity option thus creating a model reveal animation in the viewport.

In that tutorial I noticed that the animation is subject per material. I was wondering if it's possible to apply an opacity (cut out) gradient ramp to multiple materials at once so that different textures and objects on the one big object (e.g. car with different parts) can be revealed together without having to apply a gradient map to each individual material used and animating each one separately?

So the goal would be to find a simple way to apply just the one gradient ramp to the whole car and animating that.