You Can use an old paintbrush to make a stamp.
Remove the old bristles from the Metal collar, scrape inside to get as much of them out as you Can. Clear about 2 mm inside. A scalpel and sculpting tool worn best.
Use small pliers to shape the collar end like a cobble/ brick.
Squeeze gently one side then the next, squaring them off.
You Can check your shape by eye and by pressing into some resin, bluetack or similar.
To create a cobble surface cover base with green stuff, shape and smooth it, then starting at one side work from top to bottom gently pressing in shape.
Pavement edges and corners Can be sculpted on once dry.
Figures Can then be pinned once dry.
Takes some time but is effective.
Some examples on old glory blog I believe.
Don't no if that helps.