I use crochet cotton. It doesn't stretch and is very strong. I use it double and it makes a nice knot. A cruved needle works great but is not a necessity. As long as the needle has a big enough eye to get the thread through and is thin enough to go through your fabrics. I have knotted literally well over 100 quilts with 3 or 4 layers of batting for warmth and have had no problems with this. Enjoy.

Crochet thread, perle cotton, and baby yarn all work well. So does all cotton yarn but it's harder to pull through the fabric. Many also use embroidery thread and that works too. I do not like the worsted weight yarns as they are murder to get through the fabric and leaves large holes.

Just a caution- Don't use cheap polyester yarn on a cotton quilt. I made that mistake one time, and it cut itself through the backing fabric in the laundry. AAARG!

Yes! It is 100% cotton and comes in so many many different colors, and darks and lights too.
It holds the knots well.
J
PS It does not ravel or fuzz up.

I haven't seen the video.
Using long lengths of thread, I make a whole row down the quilt of double stitches with long lengths of thread between them.
Then I cut the whole row of lengths of stitches in their middles - halfway between each stitch.
Then I tie each knot using a square knot, doubling it if you like, (all the knots in the row at once) and finally trim the ends short all at once too.
It saves a lot of time, because you are not picking up and laying down your tools so many times per row.
Jeannie

I've used very thin satin ribbon (like the $1/spool kind at JoAnn) and tied lots of bows (tacked to prevent untying) for girl quilts or simple knots for boy quilts

I always use a double thread when tieing a quilt.

pearle cotton thread works well also...

I just finished my quilt last night. I used six strand embroidery floss and a curved upholstery needle - worked well!

The ribbon ties make such an elegant quilt.
So far, they wash well too! Didn't expect that!
My favorite is 1/8" narrow. Comes in lots of colors!
J