as a newly promoted specialist who has intentions of going to a promotion board ASAP,what would be the most beneficial way to study?

If you just Pinned, you got some time before you are eligible to go. Learn leadership traits that are successful to you before trying to lead others.

SPC (Join to see) armystudyguide.com is your best source. My wife was my biggest asset because she would ask me questions from it. I had it all printed out, and she would just randomly ask questions. Also, learn the Creed of the Non-commissioned Officer. You will also need for WLC because you will say it every day. BTW congrats on the promotion.

Get the MOI for the board. Theyll have the topics they'll be covering in the board. Make sure you study the updated material. I suggest going to the Soldier of the Month board. Have your NCOs run mock boards for you.