As a non-drinker of alcohol, I'll pass on helping with the sensory evaluations. But I would come visit you to "help you set up the methods."
Milk is very thick, and could sour and clog filter paper in the time that it takes for it to slowly go through. If the beverages are thicker than milk it will go even slower. Using a Büchner funnel with a vacuum flask or outlet might help, as well as doing this in the cold.
If I were to devise a test, I would do one of these:
1. dilute the beverage about 3 times with water ( 1 part beverage, 2 parts water) but filter 3 times the volume. You will get the same result, but it should filter faster.
2. purchase a hand-driven centrifuge and centrifuge samples of the beverage. The glass will go do the bottom. You will need to remove almost all of the liquid by hand when it is done. There are disposable dropping pipettes that you can use to suck off the top.
With both tests, I would think that you need to put any glass found onto a microscope to check. I would make sure that for method 2 that you analyze enough volume to be sure that you catch any glass, but always express any results by # of glass fragments per unit volume.
You may need to see if these methods have been used and validated. If not, you should be able to validate them for your use if you add a known amount of glass to some clean beverage in several concentrations and several replicates and show that the test is accurate and consistent.
Good luck and have fun.