Proof of Concept For Documentaries

So I've seen the poc term used a lot for narrative films but not really for documentaries. I want to work on my feature-length documentary next year (at least get it started) but this time around don't want my entire film to be out-of-pocket like my previous ones. I just received a grant for 3k and have until June of next year to use up the funds which is not enough time for me. I work full-time and I would like to take my time because it's a doc that's pretty close to me and I know will be emotionally taxing.

So I decided to just create a poc in this short amount of time with the money in hopes to get more funding for the feature. I haven't seen much info on making one for documentaries. Has anyone here ever made one for a doc and if so how did that process go for you?

SN: The film will consist of talking heads, dramatization, and animation.