I have a paddle holster for a Taurus 85. I love the hoslster except for the fact that it has a Chicago-style tension screw that seems to never be tight enough to hold itself whereit needs to be. At some point every few months, the screw comes loose and the little rubber washer falls out.
Has anyone ever tried Loc-tite or a similar product on the screw so that it holds it's tension better?

That is how I would fix it.

I have used clear finger nail polish on things, including sight screws to keep them in place.

Many years ago when my wife first saw the bottle of clear fingernail polish, and the baby-wipes in my range bag she shook her head and said, "I don't want to know". The blue Loctite works great on holster screws, also.

Do tell Don, what's the secret behind the baby wipes? Is this a super secret leading remover?

A bottle of baby wipes comes in handy when shooting at an outdoor range, or other places where water isn't available. A woman I was in a class with at Gunsite tought me that one. Myself, and the 19 other guys in the class were nodding our heads saying "Wow-good idea!". I've kept some in my range bag ever since. The first time I bought some after I got back, as my wife was unpacking the bags, she held the bottle up (we don't have kids) and asked, "Is there something I need to know?" She didn't buy my explanation at first! Tom T. does a slight variation of the same thing. He uses the individually wrapped handi-wipes for all of the students in his MN FAS classes.

Ha. I use baby wipes to wipe down the interior of my truck from time to time as well as clean dirty hands. Since I buy them in bulk (big boxes of Parents Choice baby wipes at Walmart), they're much cheaper than branded special purpose wet wipes and always useful. I keep mine in zip lock freezer bags.