I work with ropes for a living and quite honestly, although the prussik will work, its not the answer. It becomes cumbersome to move up and down and after a while the moving of the knot becomes tiresome and one ends up removing it.
I disagree...I have used and tested the system in wet and dry conditions and the system works extremely well. The only time I had trouble was when we had freezing rain which turned the rope into an icicle.I don't think there is much that would work in that situation.
When the main rope is attached slack free to both the top and bottom of the tree the prussik moves very freely up and down the main rope allowing very easy climbing.