I don't have a 401, but I do FMQ on a 15-91. It is basically the same for me tween that machine and my 3.5yr old Pfaff. Get your FMQ or darning foot in place, set your stitch length to 0, and drop your feed dogs. It take practice. I have done 12" square muslin quilt "sandwiches" with a different colored thread in the bobbin than in the needle.
Practice what speed works for you. Some people like to go fast, some not so fast- you are moving the quilt so you determine the stitch length. Move to fast and your stitches are long, move to slow and they get very short. It may also need some tension adjusting. That is why the two different colors of thread.
Get some sandwiches made up, put some music on, and go with the flow!