Apparently there's no way a modern domestic machine will sew denim the way my vintage machines did. They just powered through it until I got to the buttonholes.
I was chuffed that I had the 411g and the key hole buttonholer attachment until I attempted to do this. I broke three needles: Four layers of denim is too heavy for the attachment to drag around so I lifted the weight away. It still wouldn't move the fabric so I assisted and this bent the needle just enough to deflect it right onto the needle plate as it descended. Tried various ways of making it easier for the 411 then gave up on it. Took the coffin lid from the 1891 VS2 treadle and attached the 1950s buttonholer. A few minutes later I was looking at several perfect buttonholes! Yes, ol' faithful came through for me again.
The belt was also made. Pattern maker had a kit from the 1970s or '80s for a belt, so I made it out of leftover denim. It looked so good I didn't recognise it the next day, thinking she'd gotten a proper one from her mum's.
and the front
The main technique (which I'd adopted anyway) is to hand baste before machine sewing. I read somewhere that you should pin, hand baste then sew (by machine) so that's what I've done for a while now, and I have to say it's a lot easier to get a good result. Slow and steady wins the race. No longer am I interested in short cuts to get a garment finished quickly: It always leads to something I'm not proud of, or having to re-do over and over so it was never going to be worth it.