How to make a custom post template for all posts in a route?

Hi! I’m working on a custom theme. I’ve pretty much got it figure out /except/ that I need some posts rendered differently than others. My routes.yaml looks like this:

collections:
  /products/:
     permalink: /products/{slug}/
     template: storefront
     filter: primary_tag:products
  /:
     permalink: /{slug}/
     template: index

That’s working great to get mydomain.tld/products rendered with the ‘storefront.hbs’ template.
Where I’m stumped is how to by default render the items in that route (i.e. mydomain.tld/products/post_slug) using a custom file. (I know I can create a custom-whatever.hbs and then select it on the individual post page. But I want all the posts to get the custom template automatically.)

Is my best option to edit post.hbs to detect what the current route is and to change the rendering there? Or is there a better way I’m overlooking?

For anyone interested, here’s the WIP: A shopping experience for Ghost