In the past I used a few treatments to have things look a little preworn. The best was a hand rubbed oil finish that just seeped into all the crevices of the textures and made everything look a bit old. Because it was hand applied it was nice and random. Starting with an off white color for the rubber also helps.
This is totally possible and I recall seeing it a lot back around 2007 when distressed shoes were pretty popular. As Michael mentioned, usually it’s a hand finishing process. Similar to how dress shoes are “burnished” with paint wiped on and off. Sometimes the shoe is also scuffed on a buffing wheel or with a grinding disc like a dremel.
You had it right the first time, vulcanized. Also sometimes called autoclaved. This is the way the Chuck Taylor is made. Uncured die cut and extruded rubber bits are hand placed onto the lasted upper and compression molded outsole, and then put in an autoclave to cure.
It is a really old process (obviously since the Chuck Taylor has been using it for almost 100 years). Sometimes products that look vulcanized are actually “cold cemented”. That is cured rubber strips that are then cemented on. Or sometimes they are just really detailed “cup soles”… single piece rubber parts where the molds have different plates and dams to load colors (lots of skate shoes, and 1980’s basketball shoes, use this method. It is very very durable, but heavier and not as flexible).
One of the telltale signs to spot the “vulc” construction is that the vulcanization and autoclave process uses a lot of heat and pressure so everything shrinks just a little. It also creates a chemical bond, so the adhesion is really good! You always get that little bit of delamination in the mid foot but otherwise the rubber is super durable.
The best part is seeing it done in person. Every strip of rubber is hand laid, and since it is uncured, if the person presses too hard it will have finger indents. It is amazing to see how precise they are when they build shoes like this. Fun fact I learned when I started working at Converse, Chucks used to be made in Massachusetts, and later in Kentucky. There was a certain amount of “variation” associated with the US assembly. When everything was moved to China they were made a little too cleanly. They didn’t quite feel like Chuck Taylors. So the team bought old Kentucky production examples on eBay, highlighted the most desired “variations” and those little mistakes are duplicated on every pair. You can see it where the rubber strips overlap a little funny. That is all intentional.