Apply alpha to an object, rather than a material?

If I want a model to fade into existence, so far I have an IPO on the alpha for the material, and raytracing enabled. The problem is, the ray will pass through several points of the mesh, which results in you being able to see things such as the inside of the head through the semi-transparent material.

Is there any way to have the alpha be applied to the object itself, so that once a ray hits the object it no longer reacts to said object anymore yet can still make objects behind it visible?

Render the object on its own layer, reduce its opacity in the compositor. What you want to do is a 2D effect, so it should be handled in a 2D manner.

Could you elaborate a little further? I’m still learning how to use blender and there are many features which are alien to me.