Painting in Progress: Commission

I recently began a commission piece for my sister's friend. It combines 2 things I love... trains and sentimental old photos. This is a really great photo and I hope my finished painting can live up to the personal attachment that it has for her.

In terms of process, sometimes I start with one overall color underneath everything, but I didn't really do that this time. I am simply trying to get close to what I want the color of each part to be. The train section is actually quite complex with a lot of tiny parts and also a lot of texture/rust/etc. which is always a challenge. To start I focused on the background hills and trees. It's easier to get that out of the way right off the bat. I still have some more work to do on the things in the distance, but this is just the first pass.

Here is the original that I am working from: