A couple features that are a big help: 1) A machine that will sew slowly and at variable speeds, using pressure on the foot pedal; and 2) A hand wheel on the right hand side to help penetrate tapes and webbing. Note that when the fabric is tailored, the pins are placed parallel to where the seam will be; but before sewing, the pins are reset to be perpendicular to where the seam will be, so that the pins go under the presser foot easily. More often, the pins are removed just before they go under the presser foot.
Once the final shape and location of the seam is tailored and held in place with fine pins, I hold the seam with each hand, one in front of the presser foot, and one behind it as the seam is stitched. Having variable speeds makes it easier to get the seam stitched just right (two stitch lines for a lap felled seam). So once the seam lines have been marked, there is a lot of work done on the big ping pong table for the resetting of the pins.
Not a skilled or educated approach, but it works.
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