Yes I can explain a little more. I will give you a little more back ground on what I have done first. So I have done gloves, backpacks, shoes, athletic apparel and protective gear (knee pads, chest protection,etc). So for everything besides athletic gear was pretty straight forward. You make a techpack get your first samples which tend to be off as mentioned before but much closer then with apparel. From there you keep making revs till it is what you are looking for. As mentioned you will have to contend with the fact that it is a fabric so there is going to need to be some tailoring to get it right.
The reason I found the apparel process is different is it is far more inaccurate then the above mentioned. For everything else you can hold dimensions pretty well with in 3-4mm. With apparel you are talking the best sewers with the technical fabrics can hold about 8-10mm at best. This means you will end up with inconstancy that are noticeable. Especially once you put it on a fit model. Most companies use live people to get the fit dialed. This is great and is about the only way to get it to fit a person. But you would then make changes and due to the low tolerances a lot of other things would change. This would lead to a lot of revs. Most revs very unhelpful because they are not building on themselves. After about 5 revs that have nothing to do with the last one it gets a bit old. There are some difference in the techpack phase they use different kinds of measurements. But once someone shows you how to do this it is straight forward.
I really enjoy doing everything else on the list expect for apparel. I just found it does not fit me well. I really enjoy doing gloves and there is a lot of fit things with gloves but there fun to work on. I am really glad I got the chance to do some apparel I am better for it. I learn a lot from some very good people. That can only help me in the future. I also completely agree with the statement get to first sample as fast as possible. This rule applies to all soft goods. As mentioned for all of these things I did enjoy the hands on aspects.