In brief: I've been trying to sew a sleeve into the knit sweater for 3 hours now. (I'm sewing it in flat, will seam up the sides afterward.) Getting the front shoulder at sleeve seam to graft/mattress stitch in nicely is like playing Chopin - for, like, a non-musician.
I've done the shoulders / back yoke, stitching horizontally to vertically, with reasonable success. I've also managed to seam down the facings neatly.
I suspect / pray to the knitting goddess that mattressing 2 vertical seams will be reasonably straight forward after the vertical to horizontal - but what do I know. I didn't think it would take me 3 hours to do 3/4 of a sleeve seam. I cannot believe how many times I've ripped out the yarn. Were this a sewing project, the garment would have fallen apart by now.
On the plus side, immersion wet blocking is not difficult or scary at all, though it does take up a lot of space. You throw the knit pieces into a sink with a bit of Soak, rinse carefully, roll pieces in a towel (and then another towel) till drip-free. Finally, lie them over a dry towel on a pinnable surface, and pin according to schematic dimensions. Seriously peeps. It's not rocket science and you're not going to wreck things, even if your fibre gets very flexy with water. Just stay calm and pin to measurements. When the pieces dry, they'll be nice and flat, totally soft and even.
The Lady Grey coat taught me confidence in hand sewing. Even though knit-construction sewing is a totally different animal, and as irritating as it is right now, I wouldn't call it anxiety-provoking. I've read that some knitters loathe the construction part of sweater-making so much that they bring their blocked pieces to people to finish the job. To a totally newbie knitter, hours into the so-called dreaded task, that still seems rather extreme.
I'm saying this to myself and any first-time knitter who might read this one day: It's not difficult. It's finicky. Get yourself some tea. Put on some music. When you finally sort it out, you're going to be very happy you stayed the course.