I have a 20 cup percolator and a 6 cup. I mostly use the 6. What I found works for me is 1tbs coffee per cup. I perc about 6-7 minutes and that's it. From my experience over percing taste bad and also too hot will make it taste burnt.
If you don't use a filter you can get one of those little fine screen strainers that you hold over your mug and just pour through it. Also you can buy beans at most grocery stores and run it coarse through their grinder.
What I found with fine ground coffee is the only way to stop it from overflowing grounds from plugged up basket is to perc it slower. I hang the pot 1/2 way off the flame on lowest heat so it only percs once every 3-5 seconds. Of course a wrap filter fixes that issue entirely.
Also in a pinch you can use regular coffee filters too, the wavy kind. Just wet the middle and run it down over the stem into the basket. Then wet the rest of the filter and it will suck to the bottom of the basket. Fill with grounds then fold in just like a wrap minus the holes. It works okay. Usually I just perc no filter and then run the last cup through the mesh strainer to catch the grounds.
Edit: I almost forgot!!! If you don't use a filter wet the basket first before you put the grounds in. It really does help keep them from getting in the water.