I would definitely say that I am still refining those skills, though some things are easier for me than others. Obviously, my many years of sock knitting mean that I am quite comfortable tech editing a sock pattern, as I know the basic formula for socks backwards and forwards. I've also knit so many hats, cowls, mittens, etc. that almost any accessory pattern resides well within my comfort zone.
What's been pretty far outside of that zone is sweater patterns. I've made a fair number of sweaters in my 10+ years of knitting, but I would by no means call myself an expert - and I'm definitely not on a sock pattern level of comfort with garments.
Most of the sweaters I've knit have been seamless top-down construction, though I have made a few seamed sweaters, too. What I found challenging about tech editing sweaters was all of the many, many different types of construction (some of which I have never come across beforehand), and trying to visualize how the written directions would translate into a finished garment. I realized quickly that I would need some really good reference books to help me work through these unusual constructions, and I have found all 3 books to be helpful, not only when tech editing, but also when designing my own patterns or knitting the patterns of others. It occurred to me that others might also find these books as helpful as I have!
This book is jam packed with exactly the kind of stuff I was in need of: formulas, worksheets, schematics - all arranged by the type of construction (or "silhouettes," as the book refers to them). The focus is entirely on garments, with sweaters covered the most in-depth, although there is also a discussion of skirts and dresses in Chapter 6. You'll be amazed at how many variations there are when it comes to shoulders, armholes, necklines, and so many other little details (or perhaps you won't be...but I sure was).
Other topics covered include planning a design (taking measurements, understanding ease, etc.), choosing yarn and a pattern stitch and translating gauge and measurements into the final design, and finishing techniques such as blocking, seaming, creating buttonholes and adding zippers.
As the name would imply, this is a master's course on making sweaters, and I'm so glad I invested in a copy, which was just under $20 on Amazon (though I've seen it for less than $10 during Interweave's Hurt Book sale).
2. The Knitter's Handy Book of Sweater Patterns by Ann Budd
I've had this book for years - I believe I bought it way before I attempted my first handknit sweater. This book is great because it lists general sweater measurements for both child and adult sizes, which is helpful because part of the Tech Editor's job is to also determine whether or not the design's finished measurements are within the realm of reason (basically, we should take note as to whether or not something would be too big or too small for the given sizes).
The bulk of the book is sweater recipes which can be used at any gauge. The layout of the charts always throws me off when I am getting started, and I always have to flip to the front to reread the section on how to use them. But once I get a refresher, the patterns are easy to follow. Each style of sweater also has some variations to try (the book calls them copycats) by suggesting stitch patterns to substitute in for stockinette stitch.
There are bottom-up and top-down seamed and seamless styles to choose from; if you are looking for generic recipes for accessories, I highly recommending The Knitters' Handy Book of Patterns by Ann Budd, which employs the exact same approach to designs for hats, mittens, scarves and socks. Bonus: both books are spiral-bound, which I love!
3. The Knowledgeable Knitter by Margaret Radcliffe
I just got this book as an early birthday present and was incredibly impressed with it - just by thumbing through and glancing at a few pages, I picked up a few extremely helpful knitting tips. The section which most fascinates me is the second chapter, which talks about how to plan a project. It talks about the order of construction, cast on methods, and how to plan ahead for "perfect finishing." This last item is a really, really cool section because it shows actual knit examples of everything discussed: for example, it has a comparison of 1x1 ribbing knit 3 different ways to clearly illustrate why you would prefer one method over the other two.
Other topics covered are pattern modifications, shaping and fitting considerations and techniques, fixing mistakes, finishing techniques, borders and embellishments, and more. Everything is clearly illustrated with photos, drawings or schematics, all of which are accompanied by well worded explanations. There are case studies which cover a lot of interesting topics, my favorites being the ones which convert patterns from flat to circular and vice versa. For some of the topics - such as darts for shaping, several options are offered up for consideration, along with a discussion of why one might be advantageous over the other in a given situation.
If I had to choose one of these books to recommend to a knitter who had absolutely no interest in design or tech editing, I would definitely tell them to check out this book. This is one of those books I'll be turning to any time I get stuck on something, because I am pretty sure that it'll give me better advice that whatever random thing comes up on Google (not that there's anything wrong with turning to the interwebs for knitting help!).