If the latter option is your preference, here is how to do it. You have one of two options: a) find an alternative Android video player that does stream to Chromecast (of which there are many), or b) do it the long-winded, battery-draining way because you really have to use VLC Player. While the VLC media player for Android will eventually come with Chromecast support, it currently is not there. How to Stream VLC Player to Chromecast from an Android Device If you do not see Chromecast in your list of available devices, check that your computer and your Chromecast are on the same Wi-Fi network.
This step is where Chromecast streaming was added. Once there, click About and ensure that you are running version 3 or later.
For those who already have the VLC Player, open the application and head to the help menu.