Today i am going to tell you about creating the instant effect in Photoshop. If you are wondering that why i always use the word "Instant", because this word is so fast and we cannot risk our time in small things. Our final image can be like this..

Now lets take the image which you want to use in your project. After choosing the image we must have a suitable image of an old man to use it in our Project. I am using the image below. (this image isn't copy righted)

Now open the image you want to use and paste this old man image on it.

Decrease the opacity of the image and Drag it on a suitable place to make it fit on your image.

You can resize this image to make it fix properly.
right click on the image and click on "Free Transform".

Now remove the extra parts of the old man image with erase tool and decrease the opacity of this image as shown below.

Now remove select the old man layer and remove it from eyes, lips and other important parts. After this simply select the "Dodge Tool (O)" and color your hair to make them white. Because Old men doesn't have Black hair :D

I told you the easiest Tutorial on making Old Age Effect on Photoshop. If you want it in more advanced form then please stay tuned. I'll post it soon...