This is one of the hardest achievements in this game, but if you actually take the time and practicea couple of sections, it's pretty simple.
I unlocked this today on my third attempt after starting with a top score of 189,000, down to going into practice mode for 5 minutes and practising Solo D and F. (HARD difficulty)
Solo D is quite short but you need to use 2 hands to hit it effectively. There are 22 orange notes so use your middle finger of your strumming hand to tap the oranges while holding down the other coloured fret as usual. I kept breaking my combo here because I didn't know how fast I should tap the oranges. Once I slowed it down and figured out there was 22 oranges to tap, I managed to come out of Solo D with at least a 3x multiplier.
For Solo F, don't use 2 hands like I was doing! It's pretty easy to 1 hand the whole thing without losing your streak; if you're having trouble with it then slow it down in practice and then start speeding it up. It's important you hit the 2 star power phrases during this solo, once you hit them, use it instantly. If you have 190k+ at the end of Solo F then you're pretty much home and dry as long as you don't mess up in the easy section that follows.
As for a star power path, activate first after the YO sustain, second just after Solo D where he double notes are. third at the start of Solo F, fourth as soon as you get SP during Solo F, fifth as soon as you get it, just before the end of the song.
This is what I did and managed 229,000.