Using separator strips eliminates the need to match your braid seams. I happen to like the look of them. Although I have seen some that I liked without as well. Regardless of using them or not, it's a good idea to starch your fabric, then sew BEFORE trimming the points off. What I did for the long lines was to first draw them with chalk, then I lined up my separator strips. I creased both the braid panels and separator strips in 1/4s and pinned those. Then I pinned a lot between. It might help to use the walking foot and sew with the braid on the bottom. Once sewn, just take your time with a ruler and rotary cutter to cut the points off. Stretch out on a long table if you can, it's easier.
Good luck!