My husband couldn't swallow for two and a half years but that's from a different cause. What I want to say is if you father would like to have the feeling of something interesting his mouth, he can always rinse his mouth with whatever, like coffee, tea, etc and then spit it out. We, too, were warned about aspiration pneumonia which is when the liquid gets into the lungs. Keep an eye on his temperature if you are worried. Is there any chance of your getting hooked up with a speech and language pathologist about the swallowing?