Soak towels or paper towels and work into the tracks, let sit then remove to wipe clean.
Vacuum with brush attachments.
Q tip or toothbrush.
I spray WD40 and a toothbrush. Wipe with paper towels.
Hello. I have used soapy bucket of water and smaller handled scrub brush to loosen/remove a lot of debris in my window tracks sometimes also using a moisten paper towel or BabyWipe can help remove the residual dirt and debris left over.
OXO Good Grips Deep Clean Brush Set, Orange
These are stiffer than toothbrushes. $6 for 2 on Amazon and they are angled so you don't scrape your knuckles