Matte painting

I have a project for matte painting for which i shot a video,
i was hoping if i can get some inputs on how to go about it

My concept is inspired by these videos














Here is a screenshot of my shot in which i walk into the frame and camera pans up to the sky.


I have started with the matte painting in photoshop, i was wondering if i should key myself out using roto and then add myself in the matte painting in the shot or just use color key to replace the sky and replace with the mattepainting/set extension and zoom in with a camera in after effects after tracking the shot, though i feel if i just key out the sky i wont really get the depth of field effect as i zoom in with the camera.

Correct me if i am wrong. since i dont have the greenscreen i think i will roto myself out, then only i suppose i can get the effect of parallax compared to the method where just keying out the sky and replacing it with the mattpainting, it won;t really give the feel of parallax since the only affected by the 3d camera would be the elements in matte painting not the footage.