I also agree with what others have said, try putting the old bed on top. Put one of your old t shirts ot socks under the new bed so the dog can smell you. I always send something of mine or some old toy that has their smell on it if they have to visit my sisters overnight. (granted only twice, but it did help them settle more) If it is a real poofy sort of futon try unzipping the zip just a tiny bit to help expel the air while the dog gets it to how it likes it, then doing the zip back up.
"No amount of time can erase the memory of a good dog or cat, and no amount of masking tape can ever totally remove their fur from your couch"