I used to think couching was intimidating. I got over my fear of couching because of the first tip below. I learned it in a class from David McCaskill. Since then I discovered many other tips that make couching easier. I hope these help you as well.
David’s Tip: Start couching at the end where your couched thread comes out of the canvas and allow the other end of the couched thread to hang free. Doing this allows you to adjust your tension so that the couched thread sits perfectly on the canvas.
If you have a couched thread that cannot go through the canvas, just lay it on top. Take your first couching stitch so that it catches the end of the couched thread and secures it. Do this on the other end as well.
Couching stitches should never be so tight that they pucker the couched thread. They should be just tight enough to secure the couched thread against the canvas.
It’s OK if your couching stitches do not go in and out the same hole. If they can great!
Couching threads should be thin, as in a single strand of floss. The should match the color of the thread as closely as possible.
Matching is if you want the couching stitches to disappear. If you don’t, pick a contrasting color. If you are using a contrasting thread, remember the stitches will be seen so space them evenly.
You can, if you couched thread is thick enough, couch from underneath, just catching a tiny bit of the underside of the couched thread. This is a more finicky process.
If you are couching curves, space your stitches together more closely.
If you are stitching several lines of couched threads next to each other, don’t have the couching stitches line up; you are more likely to see them.
When you have couched areas that are uneven, like the spiral above, it’s OK to have lines of couching that are not continuous. If your couched thread can go through the canvas, bring it to the back and then back out at the new location. If it can’t go into the canvas, end the couched thread and then start it in the new location.