The better way to perform preacher curls

This is an excerpt from Massive, Muscular Arms by David Barr.

There are few exercises that benefit you more from the addition of elastic accommodating resistance. Because this exercise has an extreme force delta, typically resulting in a rest period at maximal flexion, the band helps to reveal any weaknesses you’ve induced created by this instinct. The magnitude of the stress stimulus and resulting growth makes it worth the pain of the setup and execution.

Equipment
Barbell and band(s)

Setup

1. Loop one or two bands around or through a stable low anchor point, so that they will stretch maximally at your maximal elbow flexion.
2. Loop the ends of the bands symmetrically onto the bar to provide balanced resistance.
3. Grip the bar and sit back so that your arms are fully in contact with the pad (a). Note that this does not mean that you should sit down on a seat.

Execution

1. Flex the elbow to curl the weight (b).
2. Maintain shoulder and arm position throughout.