Are you using the darning foot to FMQ or the walking foot? If you're having that much trouble following lines I'd check to make sure my feed dogs were down too. The darning foot is great for following curvy, loopy lines & the walking foot is good for straight lines. I haven't had the troubles you seem to be having, but I've tried doing FMQ several different ways. If I find a design I like & want to try, but am not sure of myself, I make it fit the area, print a copy of it & sew over it as though I were doing paper piecing. No marks on the quilt, so no one knows if it's not perfect! It's also good for getting the muscle memory down for a certain design. I have used stencils to mark my quilts before & I do some meandering, stippling & the like.