Notes from SleepyNPC on discord
Firewood% (Kill Sister Splinter while Flintslate engulfs your needle in flames)

Beastfly pogo

Aknid pogo
Silk Spear
Bell Beast [Save Quit after cutscene]

Enter Hunter’s March [Skarr Guard]
HM Flea [top left]
Rosary Necklace +120 (120) [top right]
Shakra Arena
Lure 2 Skarrwings to the top and pogo up [Skarr Guard + Spear Skarr]
Hanging Rosaries +395 (515) [Don’t loosen all at once or some will despawn]
Ant Arena [drop down to bottom left]

Swift Step Flea
Elevator Rosaries +31 (546)
Buy Deep Docks Bellway -40 (506)
DD Bellway Flea
Travel to Bonebottom

Rest at Bonebottom bench
Buy Simple Key -500 (6)
Travel to Deep Docks

Arena below Lace 
Open Simple Key door
Flintslate [right then upper left]
Go right to Far Fields

Far Fields Flea [Up left then up right]
Save Quit to Bonebottom
Equip Flintslate
Travel to Marrow

Up to Marrow Flea [from platform sprint jump→dash→pogo→dash→spear→down dash]
Go down to travel with Mooshka

Go through Shellwood
Garama skip
Go top right [until path blocked by thorns]
Kill Sister Splinter with Flintslate active