The basic idea is to cast Eternal Flame for one Holy Power on the non-tank players in the group. So Holy-Shock on cooldown, put a small EF on someone. And keep doing this to make sure that all five players have an Eternal Flame on them. With Beacon of Light, half the heal transfers to the tank, so the tank is getting a constant stream of small heals.
As well, Eternal Flame keeps renewing and building your Mastery shield on the players. It constantly ticks, so the shield timer renews and does not expire, and the shield can build up to quite a significant value. This greatly blunts the occasional damage that non-tanks take in heroics.
As well, it's extremely mana-efficient. HS-EF costs pretty much nothing. So you can do a great deal of healing for very little mana. I've done entire Heroics where I have not dropped below 80% mana, and that's without any raid gear other than quest boots from Sha of Anger.
As well, EF blanketing works very nicely with Blessing of Sacrifice as the shield and HoT on you will take care of a lot of the sacrifice damage. With Divine Plea, you'll occasionally get free 3-pt Eternal Flames that you can roll on people, which makes life even more stable.
Of course, when damage starts being serious, you will have to step up with larger spells. But I've found that EF blanketing makes everything feel more stable, and not as immediate. Frankly, it makes healing heroics significantly easier.
Now, is this a good idea for raids? I rather doubt it. You really cannot roll EF on more than five or so people, and the HoT is only 1-point, so it is somewhat weak in comparison to real HoTs. In a raid, if you use Eternal Flame, I think it would be better to build to 3-point Eternal Flames and keep them running on the tanks. Let the druids blanket the raid in HoTs. That's their strength.
But for Heroics, where you're the only healer, EF blanketing can make life a lot easier, dampening the incoming damage, and allowing you to leverage your strong Mastery on the non-tanks who only take damage sporadically.