How to convert finalized Illustrator illustration to line illustration?

[Wammes.ai]

Hello everyone,

I create illustrations in Illustrator with colours and shapes like in the example of the Kanye West illustration below. The other day I was experimenting trying to convert the illustration into a line drawing and I ended up with a simple "Command + Y" which resulted in the other example below. I thought it was cool and I tried to save it as a PDF to be able to print it someday but soon I learned the PDF would end up looking the same as the original illustration. Now I am wondering, how can I convert my original illustration (preferrably with a shortcut) into a similar line drawing but with the actual possibility to print it like a line drawing?

Thanks in advance!

[Doug A Roberts]

Use a single thin stroke instead of fills.

[Wammes.ai]

Well damn... Why does my brain do this to me? Thanks for your answer! Sometimes I really just don't think about the simple solutions like these.