I don't detach it. I just fold down the flip up eyepiece, then place the loupe on the glass. The waist level finder is still in place.
I do my landscape in full sunlight. The magnifier is just a higher power loupe that you can move around over the focusing screen. To get a full picture of the framing, you can flip it up, but then there is not very much shade on the glass, and it's hard for me to get a good idea of the image that way.
The standard waist level finder has a 2.5x loupe on it, which is good enough for some focusing. The magnifying hood is a 4x loupe, except attached to the hood itself. So a little harder to use.
For MY photography, the separate loupe works perfectly. I was given one when I bought my camera, it looks like these:
It is just tall enough I can place it on the glass without removing the waist level finder, I still have the shade and framing from the waist level finder, and i also have the 2.5x loupe handy which I can use to focus while still seeing the whole frame. It allows me to work fast.
With the magnifying hood, when you're looking through the eyepiece you can only see the smaller area the loupe is focused on. You have to flip it up to see the whole frame. I think that will work well for me for near subjects, like some studio shots I want to take, but for my landscape work so far I prefer a separate loupe and the WLF.
For your photography it might be different. This is just how I work and what has worked for me so far. It was what worked for the previous owner, too, which is why he bought that loupe and gave it to me with the camera.
That said, there used to be several magnifying hoods on eBay, so you might keep your eyes open for one. I'm sure more will come up. There were a lot of them brand new in the box when production stopped, and Japanese dealers seem to come across new old stock quite often.