That's probably more likely to trap grit and dirt than protect it, It'll probably be better off without anything.
Not in my experience. Both my Joplins have shock boots off an old set of Manitou SX forks. Zip tied at the top and, at the bottom, just pushed down so the first ribbed bit sits over the top of the outer tube (This means they can be easily lifted for inspection). They have worked a treat...no dirt has got in and I've run them all winter regardless of conditions. Bear in mind Joplins are notorious for failing at the first sign of dirt.