Methods/resources for improving formal/business Chinese?
You can actually work on doing this locally. I know a few of my Chinese friends who don't do business, but know every business owner in our local area and can get a decent seat at a restaurant even when people are lining up and these people aren't rich. They are just well networked.

You will need to attend local business events, not the crap your local council will put on, but the kind of stuff that business owners will attend like opening of new stores etc.

Research the different business and find out about the different stories. 

Most importantly you will need to have high quality social skills, make others feel good about themselves and build up good guanxi. Which is what you are aiming to do overseas.

If you can do it at home, then you can do it over there.