Not my script. And as such, the author and modifier has not been changed. Could not find it on the site, so I'm uploading it.
1. Install the Adblock Plus Extension for your internet browser.
2. Install the Greasemonkey Extension for your internet browser
For Chrome, you can get TamperMonkey, but keep in mind, I have not tested this script for Chrome:https://chrome.google.com/webstore/detail/tampermonkey/dhdgffkkebhmkfjojejmpbldmpobfkfo?hl=en
3. Install the Script: https://greasyfork.org/scripts/2734-youtube-whitelist-by-channel
4. Go to a video by a Channel you wish to whitelist
5. Visual Aid: http://i.imgur.com/J2lbl5e.jpg
Go to the link in the video that links to the Channel Page. Copy the URL, and then copy the string of characters in the portion of the URL after /channel/. That is the "Channel ID". Keep in mind, it WILL be a string of characters in the URL, not a simple channel name like it would be if you went to the channel page, where all the URLs simply use the username.
6. Paste the "Channel ID" to where it says "CHANNEL" into this Adblock Plus filter: @@|https://www.youtube.com/watch*user=CHANNEL
7. Go to Adblock Plus >> Filter Preferences (Shortcut: Ctrl+Shift+F)
8. Go to Custom Filters >> Exception Rules and click "Add a Filter"
9. Add your new filter. For the example in the Visual Aid, the new filter would be @@|https://www.youtube.com/watch*user=UCy1Ms_5qBTawC-k7PVjHXKQ
Done! Do your part to make sure the channels you like are paid for their hard work. Otherwise, some of them wont be able to keep entertaining you for a living.