You cut out the part that covers the feed dogs leaving the feed dogs open to operate. You mentioned you were using painter's tape. Just cut out the section of tape which covers the feed dogs leaving the tape before the feed dogs, after the feed dogs and to the right of the feed dogs.
If I can find my camera I'll take a picture for you. I use a folded index card as 1/4 seam guide. First I measured 1/4 and then I taped the card in place to the front and back of my sewing machine. Where the index card would cover the right hand feed dogs, I cut that out so the feed dog wasn't covered.