An important aspect of stitching in the ditch is stabilizing each square (or other recognizable unit) so that you can concentrate on each square as you do the free motion design quilting. You can work on each square independently if you have stitched in the ditch. It also prevents tucks on the back because of the control you have created on the front. I like to use my walking foot to STID. Lots of practice helps. Creating small projects helps with the control issues. Then, make larger ones as your skill increases.