i'd like to try this stuff:
http://betweenthelinesdesigns.com/?page_id=480
seems like spraying inside of the tunnel would be the ticket
I sprayed the inside of my 2012 Pro 600 tunnel with it last year, as well as my running boards and rear suspension brackets. It's not as good as they claim but it did help. It certainly made clearing the boards out much easier. One good stomp and it all fell off.
It is super easy to use since it is water based. It's pretty thick so it takes a cheap automotive sprayer with a bad nozzle LOL! I certainly needed a bigger nozzle than the only one I had. That was my only problem with it was trying to get it to spray out. There are no thinning recommendations that I could find. I did it pretty much towards the end of the season so I can't really comment on durability. It still looks good at this point though. It's kind of a matte black finish.
I'm still debating on whether to use it or not on my 2014. If I were to do it again I would want to drop the track completely out of the tunnel. Last time I just pulled the 4 bolts and swung the track as far forward as I could get it. I think Mountainhorse claimed in one post that he was noticing significant ice build up in the very nose of the tunnel and of course you can't get to that spot unless you pull the track completely off.