Using the Extended/Infinite Superslide (ESS or ISS for short -- What you call it is based on preference) is slightly slower than the full Superslide, but has the advantage of being able to turn in any direction. Another advantage is the ability to pull out bombs or bombchus while you are doing an ESS. This allows for a quick set up to another superslide or another trick. The direction of the ESS can be determined based on the direction you tilt the joystick. It also acts like the Superslide and Ground Jump, in that it will skip certain cutscenes such as the owl texts.
There are four known methods of starting an ESS:
During a regular Superslide, slightly tilt the joystick down to either the left or right. This must be a very slight tilt, just enough to have pressure on the joystick. At this point, you can now remove the Z and R buttons. If done correctly, Link will start to spin in a circle. Simply repress and hold Z to 'lock' in a new direction.
After performing a Megaflip, while in the air, tilt the joystick in the same way you would while you were supersliding. Upon landing, Link will start to spin in a circle. Press and hold Z to 'lock' in a direction. Important note: You must let go of Z the same frame that you do the backflip. This means while you are megaflipping in the air, the black bar at the top and bottom of the screen should not be there. Otherwise, you will only get a slow ESS.
For this method, an ESS can be started if Link jumpslashes into a wall and is recoiled at a high speed. He must also go into and come out of the water all from the jumpslash. Since he goes through the water this is sometimes called the WESS. The joystick must again be tilted slightly upon exiting the water. This is useful for an alternative forest escape as well as getting to the castle before dark when heading to Kakariko first. It should be noted that this method is faster than a normal ESS.
[ADD LINKS TO MARKET BEFORE DARK AND FOREST ESCAPE METHOD]
This is similar to the other methods, but involves tilting the joystick slightly just before getting hit from an enemy. The enemy damage must not knock Link over, such as a hit from the attacking cuccos. Note that this is slower than backwalking, and so does not have much practical use.
A HESS is known as a Hyper-Extended-Superslide. It has the exact same mechanics as an ESS, but it gives Link the same speed as a Superslide. A HESS can be set up either by activating Nayru's Love, then holding the ESS position on the joystick and putting up the shield and getting hit by a damage source (typically a bomb) or it can be activated similar to the jumpslash recoil ESS, but instead of a jumpslash, a Megaflip into and out of the water is performed.
Once the ESS is started, it can be used to continue to change direction an infinite amount of times. Simply keep the joystick where it is and let go of Z. Link will start to rotate in circles once more. Simply hold down Z again when you have the angle you want. Link can only rotate 270 degrees before the ESS will end though (Note: This is not true with the WESS or HESS), so be sure to press Z again before that rotation occurs.
If you want to go in circles clockwise, tilt the joystick slightly down and to the right (southeast direction). If you want to go in circles counter-clockwise, tilt the joystick slightly down and to the left (southwest direction). It is also possible to change circle direction by shifting the joystick from one side to the other. This should be done while you have a position locked, not while you are spinning.