i have very dark hair too. i noticed one grey hair (coarser as you say) and so i pulled it out (i'm 28). the next day i noticed three more so i pulled them out too.

i then got to reflecting on what on earth i was going to do. whether i was going to start dying my hair (can't keep pulling them out indefinately) or just leave them be.

i decided to just leave them be.

but... i don't know. i guess... i'll probably start dying my hair. i feel old. dammit.