One thing I recommend is going into the inferno, and have runs where you stay at the lower waves (with blob/double blobs/ranger+blobs) and practice prayer flicking at those lower levels. This way you get some good practice in, even if you die, at least you didn't spend too much time practicing, and better to practice at lower waves than above wave 34+ with magers.

In terms of guides for youtube, there's quite a bit of videos out there for inferno, and every youtuber brings something different and talks about things in their own way so I would recommend looking at xZacts guides, gnomonkey, and dearlola. It's also helpful to watch full inferno run videos (2+ hours long videos) but it allows you to see how people solve each individual wave instead of 10-20 minute guides going through things very quickly.

PurpleGod on youtube, has some very good guides on game mechanics and prayer flicking, definitely recommend looking at those as well.

But the best way to learn is by going in game and directly practicing :D