I transitioned from a traditional Industrial Design background (BFA of ID, designing hard goods). I found the most difficult part of the transition, was learning how to not see objects as solid forms. Basically, Industrial Designers generally design bags/packs that look like they’re injection molded or solid shapes, with a shell of fabric wrapped over top of them. You can achieve shaping via complex tailoring, but that has to be understood first. When working with other IDers on bag projects, they always ask how to “not make it look like fabric” or to have “zero fabric folding/crumpling”. So that was interesting. What I’m getting at is… you need to learn how to see an object in 3D, convert it into a flat 2D pattern and then take that 2D pattern and bring it back into 3D, in your brain (and it needs to be inside out too). Also, the manufacturing processes are completely different, using their own specialty machines/processes/factories/etc. You just have to learn it and experience it, then you’ll know it. But it is not like you’ll transition in one day.
Also- I completely agree with engelhjs, getting the first prototype is probably the 2nd most critical step in the product’s creation. First, a great design. Second, getting that prototype. Even if the prototype is 100% off, you’re still 99% closer than you were without it. You can get a new prototype made in a few days, then refine, refine, refine. I’ve worked on pack projects where we’ve gone through at least 30-40 different prototypes, just dialing in the perfect technique/construction/aesthetic/features/functions. Much more rapid than hard goods, at least if you know what you’re doing.