There are two methods of sparging; fly sparging and batch sparging. There are varied ways of doing both. I think batch sparging is the cheapest and easiest and it works just fine, but there is a debate out there. Here are a few videos on the topic.
I personally drain the entire first runnings, then add sparge water. You can also put the grain in before the water, but you still want to warm the tun up with water first. What he did to get rid of husks and grain particles is called Vorlauf. You don’t want those particles because they can add unwanted tanins to the flavor.
The next video explains vorlauf pretty good, though using the strainer is not really necessary.