Making updates to an environment that I've camera projected I have a question about camera projection that is pretty specific – forgive me if the question is basic, I'm a beginner to Blender having just migrated from Cinema 4D.

I have a photo of an old-timey street I'd like to camera project onto basic geometry to be an establishing shot. I know how to do it up to that point, but for the real shot of course I wouldn't like to use a decades-old low resolution picture. My idea would be to, once I have the projection set up, recreate the storefronts and surfaces with modern image textures, but it also doesn't feel very logical to do so in the original perspective photo when I already have that projected onto geometry in Blender and therefore can create undistorted images for, allowing for more camera movement and so on.

What would be the best way to go about this? Should I UV unwrap the projected texture and work on the unwrapped image in Photoshop, replacing the parts I want to, and then just update the texture in Blender? I feel like this would work but some of the unwrapped textures would be heavily distorted in the unwrap and hard to identify as a flattened image, so I wonder if this is a common process that can be done in a more accurate way.

Thank you!
Sounds like you're on the right track! Depending on how much detail you need to fix, Blender's UV Texture Paint can save some time between Blender and Photoshop. This tutorial goes in-depth about projecting and fixing parts of an image and provides a decent workflow.