How to get oil residue off a dslr?

I have a nikon d40 and the plastic has this shine that makes the camera look grimy. I feel like it's probably from natural oils from the skin but it would be nice to have the plastic go back to that nice matte look. Is there any cleaning solution that could restore the camera's new look?

It isn't oil - it has been polished by repeated use.

You can remove oily substances with alcohol on a Q-Tip,
but the shine is most likely the result of "involuntary polishing"
caused by normal use.

Restoring the original matte finish is essentially impossible.
A similar result could be obtained by very careful sanding
with a fine sandpaper, or by the application of a solvent
that mildly attacks the particular type of plastic each part was made from,
but neither of these fiddly methods is worth the risks they pose to the camera.