I don't have any pictures, but since nobody has replied I'll do my best to explain it. I have never dealt with muskrat glands, but I have removed mink glands fairly successfully.
With the mink skinned, or at least opened up, you will see to white spots below the tail on both sides of the vent. These are the glands. With a sharp knife, slowly cut around them until they are free. Try not to get too much meat if you can help it. It will probably be rough going for the first one (expect to knick one and watch it leak all over), but after the second you'll have it down. I have never removed the glands from a skunk, but I've been told that it is very similar (if, by chance, you've dealt with skunks). Sometimes both glands will be nice and full, sometimes one will be empty, sometimes both will be empty.
I fill a 1 oz jar half full of glycerine and squeeze what I can out of the glands into it, then throw the glands in as well. I don't sell them though, I just use them myself.
Hope this helps.
Josh
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