Trying using mousetraps, but put a bunch on there so they'll get the full effect. if that doesn't work they sell electrified pads online to keep dogs off the couches
You can go the plastic on furniture way, or there is stuff at the petstore that you can spray on that smells and taste awful to dogs. Should keep them off.
You should consider why your pets are sleeping on the furniture. Do they only have cold floor to sleep on? There are plastic mats you can purchase that are spiky and will deter the pets from the furniture. Your other option is to crate them when you are gone.