I would not use the Muenter hitch if you are not already familiar with it. It is easy to make a mistake with the Muenter hitch and wind up with no friction - just a 'biner clipped onto the rope to direct your plumet down... If you climb, by all means, learn it. I used it almost exclusively for a long time - but I was not paying for the ropes and nowadays we have much better gear readily available and hopefully don't need to get caught out without a friction brake of some sort. I have at least a figure 8 and a tube on me at all times. Tubes are cheap and easy to use; a big 8 or a recue 8 is even better. The tube is probably the easiest to figure out and it is relatively small. A stitch plate is even smaller, but I'm not crazy about using a stitch plate for a rappel.
See page 2 of
this page. This hitch is really hard on the rope - it runs on itself (study the picture). IIRC, spectra has a lower temp rating than nylon - fuses together at a lower temp and melts at a lower temp, so I don't think I would use it in spectra if I had a choice.
If the rope is large enough to rappel on, it is large enough for a Muenter hitch. But since it is very hard on the rope, a small diameter rope is going to have little or no margin of safety if you heat the 'biner up and then stop or even pause. My opinion is that only climers should consider using the Muenter hitch, although I believe it is favored by arborists.
I practice with it once or twice every outing to make sure I remember it well. I won't let students use it unless they are top roped.
My 2 cents.
Tom