I had never heard of this one before! I am going to have to try it!!!! Thank you!!!!

Interesting! What size needle?

Whatever size fits the two threads together. I normally keep a size 80/12 in my machine. I don't think I up-sized that when I used two strands of regular thread (50wt 3-ply), but maybe I went up one size. It's been awhile. You would probably want a larger size and a topstitching needle if you are sewing fast. As I mentioned, I was going slowly to do machine applique,

I do it all the time. Especially with the invisible thread when I want a strong stitch but don't want to add any color to the quilt or wallhanging tops. I have a 10 spool thread stand that sits directly on my Babylock. I place the two spools side by side and thread both through one thread hole on the stand and I tie them to an existing strand of thread already threaded on the machine. Then I guide the thread through the machine, snip off the knot and single strand of thread, and then hand thread the 2 invisible threads through the needle. When using the invisible thread, I use a 90/14 needle when quilting and binding quilts and a 80/12 microtex sharp needle when making wallhangings using very thin batting. I have a huge amount of Tex 24 poly cone thread (3-6000 yds) that I double up also. My Babylock loves it and I don't need to touch the tension. I have the Babylock Ellegante BLG and the Babylock Jane. I do this for both machines without any problems. I mainly use the Tex 24 threads in the bobbin, and I have used Maxi lock, poly thread from ThreadArt, and poly embroidery thread just fine in the bobbin. I have so much poly thread that I have not invested in any cotton thread.

I've done it lots. You need to use a top stitching needle so it's a bigger eye. I even use 2 threads on my longarm too.

I did it without any difficulty. Just upped the needle size as needed. Did some samples to see what worked best for what I was doing. Results were great.

I have used 2 threads also, especially when I wanted to emphasize a certain area.

You need to place the thread spools on the machine in such a way that one thread will come off the spool clockwise and the other counter-clockwise. That way they don't get tangled.

I just put the 2 spools on different spool holders, then hold the two threads together and give them a little twist to joint them together a bit and then thread the machine as normal, treating the 2 threads as if they are one

I can't wait to try this with two thread colors!
peace