Sewing a row or column of buttons can be a pain.
I always hate having to mark exactly where to sew them, and even then lots of times the beginning and ends aren't lined up.
So when sewing a bunch of buttonholes, like on this Jute Suit vest, I've started using masking tape.
The tape makes the start and stop markers, and then it's really easy to just draw a top and bottom buttonhole, then figure out the equidistant other buttonholes in between.
I figured it out trying to plot where buttons should go on this dress and it was a pain.
The masking tape saved a lot of measuring time and chalk.
For the curve, I just put pieces of tape along the edge to mark the 5/8" width of the tape as the border from the hem.
Then it made it easier to tape another curve the width I needed of the finished buttonhole and just mark the end buttons, the center, then the last 2 between.