Eh, the easiest way to do that bit on hard mode is to first move your hands down to the Y-B-O frets. Use the 3-2-1 fingering style for all the O-B-Y and B-Y-R and make sure you strum when necessary. Hope that helps!
Anyways, finally I can tap the TTFAF intro! However, I have like a 1/25 chance...