This might be obvious but check Youtube to see if there are any walkthroughs of the product. Some enterprise software is hard to just turn over to someone to use. They often are not self-service.

I like your idea of signing up for sales demo via website. Masquerade as a potential customer. It would be good to see how they position their product and give you some insight so you can offer suggestions on how to improve things when you get into the interview.

Good luck!