Well there are a couple types of brigade nurses:
1. ROTC Nurse Brigade Counselors
2. Standard BCT or SB Nurse
From the OERs I have seen for CPTs brigade nurse is generally listed by the senior rater as a possible opportunity. From what I know from others (not first hand) is that brigade nurses are essentially staff officers working with the surgeon and PA to ensure medic training, SRP, immunizations, medpros updates etc. From the AD nurses I have talked to it did not seem like a desirable job and I always hear of openings from my friends. You can check out the HRC website to see possible locations if they update it.
Gist of it, you do paperwork and briefs. However, I am sure everything varies with the BCT. There really isn't a lot of info on the net.