How do you free the Dragon Serpents throughout the map?

Target them, hold X.

Target them with LT, then hold X
go to
www.achievementhunter.com/games/guides/brutallegend/index.html
it is a link to a map of all the collectibles

There are two ways to free the Ball-Gagged Dragon Statues.

First way is to face them and hold down X to use Clementine's Pyro attack on them to free them.

Second way is to run towards them, but a little to the side of one, and use the Power Slide move.

So basically, if those two techniques work, I'd think any Fire-element attack will free the dragon statues.