Hoodoo work is often used by people from all walks of life because "it works". There's a reason why it works that many people don't necessarily think about.
In hoodoo, everything you do must be just. It must be approved by your spirits (be them specific Saints, God or your ancestors). Yep, you need approval of the work or the spirits may interject to stop your work or even flip it on you.
When a worker works, they have confidence because they know they have spiritual approval so there's no need to wonder if their work is going to go wrong or right.
In knowing that, let's be honest. Not everyone wants to do divination first. Not everyone has "time" and not everyone knows how. So, in that situation, what do you do?
You take your time to get your ingredients. In doing so, you are giving your spirits time to speak to you.
I rarely do divination, however I always listen to my spirits. Recently, I was put into a situation where I specifically asked my spirits to show me a different way to accomplish my goal.
It took me 1 1/2 weeks to get my ingredients all together, to pray over them, to work them up, etc. By the end of that 1 1/2 weeks, I heard them. Loudly and clearly "Don't do it. You need to let go and take what comes".
Now, had I rushed into my work, looked for the "easy ingredients", etc...I would have never heard my spirits telling me to stop because I was emotional, I was determined and I wasn't giving myself time to think. Had I done that work..I don't want to even think about what my spirits would have done.
This is why conjure workers divine first. They commune with their spirits. They listen to what's being said and they take their time. THAT is why the work works. Because there is confidence in the fact that what's being done is being done with the blessings of the spirit world.