Live Double Barreling can be a complicated (but fun) dance of reading your opponents' physical reactions to your actions and tendancies. It is more difficult to fully explain than this, but you understand it when you're doing it.
Online, it's easier to do, but the same constraints apply, you just have no physical information.
One thing that is mentioned briefly in the article under “Position is Key in Multi-way Pots” is "Keep in mind, however, that you may be forced to decide to fire a third barrel on the river". This is something you should definitely be doing any time you throw chips into the pot on a bluff, any position, any number of (potential) callers. Double barreling requires some chips, so make sure you have them. In order to have reached this position, you have raised Preflop and C-bet the Flop. Even if the second barrel doesn’t come until the River, you’ll have fired three or more times into this pot.
Another important point is : “Under no circumstances should you reduce the size of your bet. That screams weakness, and a double barrel requires an image of strength to be effective”. I see way too many people Double Barreling weak on the Turn (Excluding the 10% of them who aren’t actually Double Barreling and have turned the nuts).
As always: “Keys from your opponents” are everything. You can often find a save on the River if you can convince your opponent who did not believe you on the Flop, that you actually hit the River. This whole situation becomes a lot easier if you know what they have.