Oh dear...
This is a thorny topic. A very thorny one. I wasn't going to comment in this thread until I saw a comment you made OP that I had to respond to.
FIRST, I will start by saying I've written cultures that are not my own, so I get where you are coming from. I'm not white, but
anyone is at risk of getting things wrong when it is not "theirs."
I am of two minds.
One is, if it is possible to do the research,
do the research. Research everything and go as direct as possible from multiple sources. For instance, I wrote a character who is a Rasta, and made sure that I listened to real Rastas explain their beliefs and values, the way they understand it, "practises" etc. I felt comfortable with tackling this because I know Rastas and have a personal understanding/connection with the culture. However, even then, I didn't make it the primary focus of my story. It is an aspect, or small part of a supporting character's identity. It subtly informs his characterization but I think therein lies the difference.
Is your voodoo practitioner a main character? Is your plot centred around him/her/their beliefs?
If you find yourself saying "how do I
not this wrong" you might want to consider whether you are the best person to be broaching the topic. If you do not know what could be considered incorrect or offensive then you do not know enough. You're not ready yet.
I will commend you for asking the question, "should I be doing this" as this is the first step. But you have to realize that the answer you get may not be the one you want to hear. You asked if you should do it. *You* asked:
Is it at all okay for me to write about a religion like Vodou, or Santería, or Native American traditions?
Someone told you no. And your response was basically, "how dare you tell me I can't?"
Now while I won't go as far as saying "never write on it" you have to understand the perspective Maximal is coming from. I've heard this argument before, specifically with regards to Indigenous people (Or Native Americans, as Americans call it).
So how do you get people not in the know to respect cultures / practices not your own? You inform and educate.
While this seems innocent enough, this statement reflects a level of arrogance. I'm *NOT* saying you are arrogant, but it is inherent to a very Western worldview, the kind that informs old-school anthropologists. If you ask someone to teach about their religion/culture so you can do a better job of connecting with them that's great. If they tell you it's none of your business, respect that also. Please be aware of one thing. No one is obligated to educate you. No one is obligated to help you understand. Some spiritual practices, cultural traditions are held as sacred, so sacred that when outsiders become aware of it, it is considered a weakened. And given the history of colonialism, this is not an irrational belief. Respect should not be something a culture gets only if outsiders understand it. You can
not understand it, and still decide it is worthy of respect.
This is not just "my" opinion. This is me paraphrasing the thoughts of a Native American woman on a blog blasting JK Rowling for her careless depiction of them in her writing. I suggest you read up the responses to this controversy as well. It was/is a huge deal.
Adults write children. Humans write elves.
NO. This is NOT the perspective to take. Ignore this. Humans write elves??
Elves don't exist! Other cultures are not elements of fantasy. And adults can write children because they were children once and can easily find children to base around--just NOT a good comparison at all!
Ultimately OP, if you decide to write on this topic then know you will likely get things wrong because minority belief systems just do not have a lot of information about it just openly available to everyone. If you are so lucky as to get a sensativity/beta reader to read it over when you're done, and insider who is part of the culture, then that will help reduce the risk. Either way, be prepared to get more responses like Maximals. Not trying to be harsh, but honest. Good luck either way!