Update 4/11/18
I was surprised to receive 2 additional filters (small and medium gravity filters) in the mail with an apology note + suggestions with different coffee grinds (they recommended I use Trung Nguyen instead of Cafe Du Monde). It was a nice gesture so I've bumped up the rating. After tinkering it with a bit, I think I got them to work correctly with Cafe Du Monde. I'll try out Trung Nguyen coffee next time.
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I'm not sure if I got a defective phin, but I bought the medium size to use with the Cafe Du Monde (the most typical grinds for Vietnamese coffee) and this thing drips waaaay too fast. I have literally tried every troubleshoot (add a little water to let the grinds expand, flatten the grinds evenly, add more grinds, screw it tighter, screw it looser, etc) and every time the water filters through in less than 30 seconds. Maybe the holes are larger as you buy bigger sizes? But I'm pretty upset how much coffee I've wasted trying to figure out how to use this properly. I might see how the small size is, or even see if the gravity filter will be better. But sucks how there are no returns.

Having this for a month, making great coffee with condense milk, love it.
Learning different ways to make coffee around the world is very interesting. You may want to check them out.

This method is to screw down to press the ground coffee. Do not forget to loosen a bit before pouring hot water! If not, it will be stuck with the wet coffee and you will have hard time to release it back to clean. Al little coffee will somehow drop through the bottom holes, you may want to shake a bit to reduce them before placing on your cup. I use a Japanese tea strainer to catch the used coffee,to keep them from going down the drain (it will plug the pipe, they say)

As it's origin, I think the coffee harvested in Vietnam makes the best taste with condense milk! Especially over ice.

Specialty coffee gadget for brewing Vietnamese iced coffee, and/or conveniently placing on top of cup for hot coffee. Brews coffee similarly to a french press combined with pour over. Method is to pour hot water through tightly packed coffee grounds. Advantages over a french press are that you can make smaller amounts, brew directly over ice and condensed milk, and the stainless steel is more durable than a glass french press. Disadvantages are volume, and the handle can get a little hot, but those are minor. Can be used with any ground coffee, so it's not necessary to buy specialty coffee unless you want to experiment with the unique flavor of Vietnamese coffees.
This brand is well-made.

1. use cafe du monde coffee, this is likely the closest flavor to what you think of as Vietnamese coffee in America
2. wet the coffee in the bottom with water 1/4th of the way up without the filter screwed down, this will allow the coffee to expand into a paste and greatly increase reduce water going through.
3. once coffee is wet and expanded, smooth with finger/spoon so coffee paste is level and there's no pockets water can go through, and screw down the top filter onto paste so it is compact and snug as can be. this will prevent the coffee from just pouring down through where ever air pockets are.
4. then fill the coffee container with water all the way up to the top, it should go through much slower and be much stronger, about 4 minutes

This coffee maker relies on a slow drip, about 4-5 minutes. I heat water up to boiling point. Then grind the beans at a medium grind , put base filter in pot, pour coffee over this filter and try to get the grinds level in the pot. A small tamper would work here. I am still working on this. Then screw the top filter on to stem of bottom filter. But not too tight or water may not get through. Try screwing down the top filter just enough to touch the grounds. Then pour in at least one cup of hot water. Back up: The pot needs to sit on top of coffee mug or glass, then pour water over it. Cover while dripping to save flavor. You can add milk before or after water is added, if you use it. This procedures is WELL worth the wait, because the flavor does not have the sharp bite that high pressure espresso machines can create. The result is strong but mellow! And that IS incredible! Ed