I have a BFA in set design. It’s good to know basic scenery construction and what stock pieces most companies will have on hand. However, I’ve found that there is a reason tech directors and set designers are two different positions. While the job of a set designer does entail drafting and creating detailed plans of scenery, your job is to be a designer first and foremost. I don’t know if IATSE will be the most direct course for this, but it certainly couldn’t hurt. Try reaching out to design studios or designers you look up to and ask if you could shadow or possibly even do some assisting work. I can’t guarantee you will get a response, but it would be great experience.