go hard, see what you can do. keep struggling through it, then once you start to lose stuff, go to medium. Play most of medium, then go back to hard.
Once you get close to the end of hard, jump to expert, play expert as far as you can. When you get stuck, drop back to hard. I think forcing yourself to play harder modes you struggle with, then dropping down helps A LOT.
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[ ] 5/6 Star Expert Guitar (~125/137)
[x] finish expert drums
[x] FC DOA (with screaming correctly)
[x] expert vocals all beaten
[x] finish endless setlist (expert)
[x] 5* GGaHT