When arriving in Vietnam, Chinese was already on my mind and I've been learning both languages in parallel, thus always comparing them. First I tried to identify the common vocabulary, then I discovered the ancient local Nôm characters. Later i listed out how words common in Chinese and Vietnamese (Hán Việt) were nearly systematically paired with words of local Vietnamese origin (Thuần Việt)
e.g.: 水=Thủy<>Nước, 马=Mã<>Ngựa, 人=Nhân<>Người, etc.
I imagined a system called "Binary Nom" where Thuan Viet were defined based on their Han Viet counterpart.

It evolved into something not strictly binary, since Han Viet words often came with several variations corresponding to multiple borrowings from China (e.g.: 及 Cập, but also Gặp and Kịp). Besides, other notable borrowings we made from French, leading to triangular lexicon:
包=Bao<>Túi<>Xách="sac" in French.

Finally i came out with this document: Introduction to Neo-Nom 
It presents a method to transcribe Vietnamese into modern Chinese characters, in order to immediately show the equivalences between the two languages. The aim is to help people learning either language to make connections with the other.

(NB: this article has some Chinese characters. It is useful to use a pop-up Chinese dictionary, giving meanings and pronunciations. You can also open the above pdf in your explorer to use the popup dictionary in the pdf itself. I recommend "Mandarin popup" with Firefox.)

Example:
Tất cả mọi người sinh ra đều được tự do và bình đẳng về nhân phẩm và quyền lợi.
毕全每人生出都得自由与平等回人品与权利。


Yesterday I also realized that I accumulated enough data be able to quickly create this automated transcripter, from Vietnamese to Neo-Nom !
https://lingojam.com/VietnamesetoNeoNom

In the above transcription into sinograms, those representing words not related to Chinese (Thuan viet) are marked with a star.