Does anyone know of a product that I can apply over a knot to make it smoother.  I fly fish some and whenever I add a new length of tippet to a leader, the subsequent knot will invariably snag on or pick up algae or vegitation.  Will fingernail polish work?  I already trim the line as close to the knot as I dare.

Fly tying head cement will work. I don't use a tippet, I prefer a 9' tapered leader. They are kind of expensive, but I am spoiled with them. You can get head cement at any fly fishing shop or on line. I think it will help your situation.

Ronnie