Everyone knows they're fake. If they're already fake looking, you may as well make them look like they're supposed to be that way.
I take my fake pumpkin and paint black lines in the creases. Before it can dry, I apply metallic copper paint in between the black lines. Working with one or two "stripes" of copper paint at a time, get your paint brush wet and go over the area, letting the water blend the two colors a bit. (Do not use a foam brush for this project.)
Continue the process until the entire pumpkin is completely covered.
I spray an indoor-outdoor clear sealant on the pumpkins once they're dry.
You can leave them at that, or paint/stencil a word (blessings, thankful), your address, etc.
Now it's out in the open that they're fake pumpkins. No more pretending to be something they're not...