I have not done Marti Michell's method, but I have a book, Divide and Conquer! Quilt it Your Way that I used for a quilt that was too large for me to handle. On that one, you make the whole top, then you sandwich it. Then, you cut 1/3 of the batting off on each side. You quilt the center, then add the batting on one side and quilt it and then the other. The advantage is that you don't have all that bulk to deal with at one time.
They tell you to cut the batting in a wavy line, so that you can line it up. I had no luck with that and wished I had just cut it straight. The iron on fusing that I used to join the sections of batting didn't work well. I used batting with a scrim and it didn't like the iron, so I ended up zig-zaging the batting sections together. Had I planned on using the zagzag to join the sections, it would have been ok, not great, but ok. Once the quilt was done, you couldn't tell any difference. It was just frustrating.
I think there are patterns that lend themselves to the "quilting in sections" idea better than others. One is the French Braid. With sashing, it would be easy to do. I would suggest you pick a pattern that is actually designed for quilt as you go.
Mine worked out, but I haven't done it again.
bkay