Photographs tend to clump values at both ends of the scale and wrinkles stand out and appear exaggerated.
When you're painting someone with wrinkles - know that they always look worse in a photograph than in person.
This is the same photo after I took out some of those dratted wrinkles via Photoshop. Per usual, I've exaggerated to make the point.
So here are two examples and you can see how to tone down those wrinkles step by step.
It will help to make your reference photos more flattering- and still be accurate.
I work in "Layers" in Photoshop.
I create two duplicate layers of the original photo.
I turn off the "eye" on the top layer and highlight the second layer.
I select Gaussian Blur filter.
In order to demonstrate this I have exaggerated the filter.
Next I make the top layer visible and highlight it.
I'll then select the eraser tool to wipe out all the wrinkles - being careful to leave specific and detailed features - eyes, nose, mouth, hair, etc.
Then move to the middle layer and adjust the opacity.
Again, I have exaggerated here to make a point - but you want to make it "believable."
When you like the result, flatten the image.
Here's another example: