I feel that my interpersonal skills could use some work. What methods or resources do you use to brush up on your interpersonal skills if you're not a natural social butterfly?
I think you're looking at it the wrong way, if the job became toxic enough for you to quit, then your previous 'finesse' with dealing with people wasn't working too well. The workplace is a totally different environment from college, you need to acquire a different set of people skills particularly as youngster.
Mostly these are about keeping your head down and absorbing as much as you can. Dealing with arrogance and a lack of interest in your issues and lack of faith in your abilities is sometimes par for the course..