I'd never hand over thumbnailing (where I'm deciding what the scene will look like), linework (because if someone else does it, it won't look like MY art), or coloring (see again, won't look like my art if I don't do it... and I can't have someone else flat with markers, unfortunately!), but I WOULD theoretically let someone else ink (and especially re-ink) if they have a style of inkwork similar to how I do mine.
Scanning and editing I'd gladly hand off, though. PLEASE let someone else deal with scanning, color-correcting, cleaning up the gutters and margins, fixing small errors, and putting in the text! This process does not spark joy!!