I feel the need to point out that regardless of how you're "pre-warming" the cache, you're missing the primary benefit of page caching.

By default, Rails' page caching persists to disk. An immense advantage of this solution is that you can use your web server to serve these pages directly, without ever hitting the Rails stack.

You're saving the page generation time, but you're still hitting the Rails stack + Redis for every single page request, both of which are entirely unnecessary.