The 2 main things your are probably having problems with is Raining Blood's Mosh 1 and the Lou Boss Battle. There is a video embedded at the bottom which shows a handy glitch which will allow you to beat Lou within seconds and it works on any difficulty but first...
Basically hitting the first 2 SP phrases is key, survive for as long as you can before hitting the SP (hit it using the select button on your guitar as it gives you more control over when you activate it, if your'e using a GH3 Les Paul or RB Fender use your palm, if your'e using a GH:WT guitar then it's the real easy, if you're using a GH2 Xplorer then your shit outta luck).
Strum the first note of each quad and try hit as much of it as you can, when you get the 2 chords and a random yellow note ignore the 2nd chord and the random yellow note.
After this there's nothing you shouldn't be able to pass if you have gotten this far, if your'e paranoid same the rest of the SP for the trills (the patterns that go like R,Y,R,Y,R,Y or G,R,G,R,G etc.) in the flood and just anchor the left most colour (right most for lefties) and tap the other colour as fast as you can while strumming fast.
LOU GUITAR BATTLE:
[[Credit goes to xlyo345 on YouTube]]
Step 1. Sign into your profile.
Step 2. While at the main menu go to options, then go to Cheats.
Step 3. Enter the cheat for "Easy Expert" and "No Fail."
Step 4. Turn on ONLY those two cheats.
Step 5. Go back to the main menu, select Quickplay, Expert Difficulty
Step 6. Play Through the fire and flames and get to the part after the intro.
Step 7. Pause, Quit,Go Back to the Main Menu
Step 8. Sign Out of your profile.
Step 9. Sign Back In, and go into your career, go straight to the Lou battle, and Start it!!!!!
Step 10. Once the battle starts, watch Lou's rock meter. HE FAILS!!!
Step 11. Finish Him!!!!!!!!!!!!
Green + Red, Green + Yellow, Yellow + Blue, Red + Blue,
Blue + Orange, Yellow + Orange, Red + Yellow, Red + Blue.
Green + Red, Blue, Green + Red, Green + Yellow, Blue,
Green + Yellow, Red + Yellow, Orange, Red + Yellow, Green + Yellow,
Yellow, Green + Yellow, Green + Red