awesome work, I've been wanting to create something like this for a while and just looking at your flow has explained a lot, thanks for the insight. the composting i have been doing looks very illustrated but yours is very very true to life.
I loved how you mixed so many images for the sky and landscape! Usually when I work I try to use less images for each part because I have a hard time mixing so many different images together. But you have encouraged me to start using more images, so I will give it a try next time I have to make a photomanip
When I mix my images, I mainly use the curves filter along with color balance and sometimes hue/saturation. You can pretty much do anything with the Curves if you play with the Red Green and Blue. At first I clip them so I can re-adjust them later on if they weren't alright. Then, when my file become too big I merge them all and save it as a new file.
Really nice man, yeah I can see marvels can be done using those tools. I usually use curves a lot too but I will start playing with the RGB more. The balance tool I just started to use it recently along with vibrance, really helpfull too.
But I can see a lot of masking and some painting in your works that really make them stand out. The masking is specially important I think, not only to crop some parts of an image, but to apply color correction and other effects to the parts you need to.