To play Russell Lissack's ingenious opening riff, you need two delay pedals set up in the effects loops of a line selector such as the Boss LS-2.
Alternatively, a multi-effects pedal set up with delays on two patches will do the job, provided you have a footswitch to control them. One delay should be set up to repeat constant 16th notes (103ms) while the other sounds eighth notes (205ms). The tempo is 146bpm.
There are very few actual notes to play; the delay pedals take care of most of the sound, repeating each note over and over. However, make sure you pay attention to your pick-hand muting. Each note needs to be kept short in order to produce clean, precise repeats.
The hardest aspect of the riff is the constant switching between the delay pedals. Make sure you let the full sequence of repeats finish, but also switch delay in time to catch the first note of the next sequence.
Lissack's tone is clean but with some bite coming through on the diads. To achieve this, use a guitar equipped with single-coil pickups and pick with sharp, forceful upstrokes. The delay setup is far more crucial than the basic tone, though.
You need to be able to switch between two independent delays, ie, the first delay effect must be bypassed when you switch to the second and vice versa.