@musicshahram, glad to here object caching is helping you for now. Memcached objects typically don't expire as quickly as static page caching does so I think you'll probably be surprised at how well this will help your server / database performance for the long run.
For priming the cache, you may look at Optimus Cache Prime - https://patrickmn.com/projects/ocp/
Someone wrote a warm.php script - http://www.pixelenvision.com/1572/php-cache-warmer-preloader-for-w3-total-cache/
I'm also pretty sure that W3TC has a cache priming feature - https://wordpress.org/plugins/w3-total-cache/
Best of luck!