Working on the whole image

Here you can see a view of the entire image. I'm working at 300 PPI and the size is 12"x9." It's a pretty big image, but the complexity of the refinery portion really bogs Photoshop down. I'm using lots of vector Shape layers to create the tangles system of pipes and structural elements. Also included is a detailed shot of the refinery itself. Because the view is from overhead, I'm using 3-point perspective. A separate Shape layer contains thin vector lines going to each vanishing point. Because they are comprised of vectors, I can reposition them as I need. All I can say is that painting a refinery (or whatever this is) is a lot harder and more time-consuming than I had expected. This part of the illustration may end up taking the most time, but ironically, it's not really that important. It just hast to be there. The important stuff will be in the foreground and is yet to be done.