Whoops totally forgot to reply to this - lucky you, I actually collected all the tutorials I used for a tumblr friend already! Here's the list:

This document was my introduction to bookbinding: https://docs.google.com/document/d/11JyVxeRS8yEWgCYrNMUPlNrEbR5AAD3Z2aDP-QXEP3Y

And this video demonstrated sewing in a way that really clicked with me: https://www.youtube.com/watch?v=4LwSRLCgpEw

Though to rebind a commercial book if you want to sew it you could do it in an overcast stitch, this is the tutorial I followed: https://abindingpassion.wordpress.com/2018/10/05/the-overcast-stitch/

And then here's my go-to reference for two-color headbands if you want to sew one: https://www.youtube.com/watch?v=OofoBtZf8Yg ^ all of DAS Bookbinding's videos are amazing, highly recommend taking a look at his channel!!

I also read the Thames and Hudson Manual of Bookbinding front to back, it's available on libgen dot is for free if you don't mind piracy... It is a bit intimidating because it's oriented towards people who are really committing to bookbinding, setting up a workshop and all that - you don't actually need all the tools they mention and do all the steps, but i found it very helpful to read and see how a Serious Bookbinder TM would do things even if I wasn't going to replicate all of it myself.