I know I should clean & sanitize anything that contacts the wine, but what about my hands? Say I'm in primary fermentation & want to grab the floating thermometer for a reading. Is pot-meta OK to spray on my hands first?
If you wash your hands and try to be conscious about cleanliness, I don't think there's much to worry about. I worked in a quality oriented, small batch commercial winery and the winemaker had no qualms about sticking his hands right in the fermenting must, squishing down fruit in the basket press with his bare feet or dipping his tasting glass right into an open fermenter. This is a man who has loads of experience working in many of the world's wine regions, and whose standards regarding cleanliness and quality were extremely high, and whose wines are truly outstanding. So I personally don't fret too much sanitizing my hands. I think sometimes we all have a tendency to get a little nuts about sanitation... don't get me wrong, I keep all my equipment clean and sanitized, and I rinse with sulfite and water before each use. But I don't believe the issue is so much to keep the must "sterile" as that is impossible, but rather to keep wild yeast and bacteria populations from building up on equipment and reaching potentially problematic levels. This is not to discourage your attempts to sanitize your hands... by all, means go ahead!!! It is far easier to prevent sanitation problems than to correct them. But I just don't think you need to worry about it too much.