When I do machine quilting with my regular sewing machine, I always go in one direction at a time...ie" to to bottom, side to side, or diagonal...depending on the quilt.
I also make sure I "tug" the area a tiny bit - while holding each side of the area going under the needle. I saw this on several videos.
The only time I'd lower the feed dog would be for FMQ, everything else has the feed dog engaged.
Also, take your time - going at a moderate speed, that works for me.