Yo,

I learned to Tornado of Souls solo a while back. If possilble, which arpeggio part are you having trouble with? Is the the three strings accending ones, cause if so, he does not sweep on that part. He just down picks very fast.

But if you mean that 4 string sweep with alot of legato at towards the end, then I recomend learning the sweep with out doing legato, or less legato to make is simpler.
e|-------------------------------------|
B|--------------8h11/14p11------------|
G|------------9------------12----------|
D|----8h11-11----------------14-12----|
A|-/9------------------------------14--|
E|-------------------------------------|

play this for practice:

Each fret finger corresponds with each fret.
M I M R/R I M R I R
e|-----------------------------------------------|
B|----------- -----11(R)/14(R) p11(I)----------------|
G|--------------9(M)-------------------12(M)-----------------|
D|---8(I) h11(R)---------------------------14(R) p12(I)-----|
A|-9(M)---------------------------------------------14(R)--------|
E|-----------------------------------------------|

[U]FRET HAND FINGERING[/U]
I = Index Finger
M = Middle Finger
R = Ring Finger

It sounds basically the same. And once you can do that, then the original shouldnt be to hard.