The amp model is custom, so I don't know what the person started with. The gain is all the way up.
The tone settings are as follows: Bass: 3 (or about 1 o'clock) Mid: ALL THE WAY UP (Randy boosted his midrange alot) Treble: 4 (or 2 o'clock).
EFFECTS
Compressor: Threshold: 50 Gain:3
Chorus: Speed: 20 Depth: 3 Pre-Delay: 10 (The chorus is the key to getting that thick sound)
If you have a noise gate, that'll definitely need to be used. This is a very high-gain setting, and is prone to feeding back when turned up and played close to the amp. Alot of my friends comment on how close this is to the real thing. I've been trying for YEARS to get even somewhere near close to that sound, and now I have it. I hope this helped even a little and gets you what you're looking for.
For a quick snack, picks is good eatin'