To get from Santiago to Pucon is a ten hours busride, but if you time so that you land at night and get the night bus it is really no pain at all..My experience is that Tur-Bus is a good ride, they charge a little extra for the kayak, but notthing too bad. I have taken the bus from Buenos Aires to Santiago, with a kayak, and thought it is not a bad ride, I thik I would pay the 300 dollars extra to get to Santiago right way.
If you have a kayak with you then it is quite easy to pay a little for shuttle with the raft companies in Pucon, or head over to KayakPucons little shop and rent a guide for a few days.
Of course this whole trip depends on your river skills, are you a good kayaker that can go on class four rivers? Because Chile is a heaven for that stuff... Especially around Pucon. If you enjoy the class fives, well even better. You can rent a creek boat in Pucon, but if you can get one on the plane I would rather just bring my own... After all, you could even sell it at the end of your trip down there.
now if you really want to do it nicely, then you rent a car in Santiago for your stay... A Pick up is usually 80 to a 100 dollars a day, so if you are a few people together it would be the best. You can camp a lot of places for cheap.
Food and accomodation is not that cheap I find.
Chile is one of the most amazing countries in the world, and I highly recommend going there. The futaleufu is amazing, though can be cold and running high well into January. Better go with someone that knows it!
I am happy to supply as much info about this amazing country as needed, so please drop me an email at firstname.lastname@example.org
if something is unclear. After eight years of travelling in Chile I have learned a few tricks... And if not, I might see you guys down there, I leave for Chile on Thursday...