After removing the buildings and road surface, I began by cutting new templates for all the footpaths and road surfaces.
The template cardboard will end up as the base for all my footpaths and roads. Folding the printouts around the templates gives me a even hard surface to work on. I then enlarged the footpath on one of the streets by adding a balsawood infill.
I also like to add extras, like sewer drains and road gutter drains, once again checking that the vehicles fit. It's also good for hiding faults.
I then returned the buildings, cars, people, and street extras.