I zigzag on my DSM too, never had an issue with getting it in the feed dogs.

I use tissue paper for some paper piecing and that is what I use to make sure the batting doesn't get caught in the foot dogs. I just butt up together as it goes through and a large zig-zag stitch. Tissue paper is easy to tear away. Works for me!

I place the two pieces of batting with a slight overlap and then cut it through the overlap using my rotary cutter and ruler. By doing it this way I have two matching edges that lay flat. I usually whip stitch it by hand but have also zig zagged it on the machine too. I enjoy doing hand sewing so prefer to whip stitch it. The price of the iron on joining strips has shied me away from using them. I always use warm and natural so I can't speak for other kinds of batting. No batting goes to waste around my house.

i just did this this week. Thought I'd come up with something new. I really like using the interfacing and it's a lot cheaper too.

I am able to zigzag the poly batting with not too much problem. If a small bit gets caught up, I can usually snip a couple of fibers without any issue. I have been known to use a 6" ruler to assist in holding it down. Works pretty good.

I bought a foot, I think it is an edging foot. It looks like a blind hem stitch foot, with a flange in the middle, but no curve. Works really beautifully for joining pieces, very flat, no overlap.

I use a wide zigzag. This is also a good way to use up partial bobbins.

Same here! Large zigzag...does the trick!

I use light fusible interfacing cut into strips to join. I cut in a curving shape and but the curves up to each other so there isn't any straight visible seam line - use a pressing cloth - adhere fusible interfacing over the seam to join. :)