How to set or change page content from Filter or Event.

[Twiggled]

I want to change some content of my pages before it is displayed but i have tried the codes below but no changes seem to happen either using Filter or Event. Below are what i have tried separately but none of them seem to work.

class Filter
{
public static function ipSendResponse($response)
{
if (is_object($response) && $response instanceof \Ip\Response\Layout) {
$response->setContent('DUMMY CONTENT');
}

    return $response;
}

}

class Event
{
public static function ipBeforeResponseSent($response)
{
$response->setContent('DUMMY CONTENT');
}
}

what am i doing wrong and what is the best way to change the entire content on a page?
Also this is a Multisite Site. If that makes a difference.