Basically, I'm making a lot of progress drawing in buildings and upgrading sidewalks to modern standards in my city, but sometimes I lose track of what I have and haven't done yet. As simple as highlighting the areas I've finished in a colour, is there a way I could track this? I'm willing to use any kind of tool for the job.
I once had to place a bunch of different stuff on a video game map. To keep track of where I'd been, I loaded a picture of the game map into Photoshop and made a new layer (partially transparent) so I could color in areas once I was finished with them.
Photoshop itself is obviously massively overkill for this, but it did work pretty well. Transparency and either the brush or lasso-and-fill is all you really need.