libgen (definite #1) + open courseware + youtube for occasional novel practicalities + open source scientific/engineering software and hardware communities. I'v

libgen (definite #1) + open courseware + youtube for occasional novel practicalities + open source scientific/engineering software and hardware communities. I've gained solid professional competency in entire branches of engineering with these resources. A teacher also helps. Don't be afraid to pay a consultant to mentor you in difficult areas with high iteration costs.