Dan, this happens a lot. As the wine ferments, the skins will float to the top (and become the "cap") and you will punch this down a couple times a day. If I need to draw a sample, I take a large kitchen strainer and push it down into the wine, not quite submerged. The wine in the strainer will be free of skins and most debris and can be drawn out with a wine thief or kitchen baster. At the end of fermentation, when I move to a carboy or barrel, I scoop the cap off as best I can with the strainer (and press these skins) and draw out the wine through the spigot. It will still clog now and then and have to be cleared with a long spoon from the inside, turning the spigot on and off a few times or you may have to siphon with a large diameter hose. I have seen a device, not sure what it was called, but was a little mesh protector that you would have to put around the spigot inside the fermenter before you start the wine. I have never used this nor do I know how well it would work.