Try lying down next to the couch or wherever one is hiding and just extend an arm or hand but then turn your face away at the same time to take away the "threat" (you know, of being eaten- you are the potential predator! ha ha) When you do make eye contact, make long blinks, and try to open your eyes having them looking to the side, not at the cat. keep your teeth covered with your lips. And believe it or not, baby talk was scientifically proven to appeal to animals as it does to babies, so don't feel silly! The eye and teeth thing is how animals communicate- I learned back when socializing feral cats and still use on my semi-ferals that I have had as pets for several years when i want them to tolerate brushing and nail-clipping! They LOVE long blinks and often doze off while we exchange these. Don't forget the most important thing of all FOOD. Sit on the floor where they are hiding eating a delicious roast beef or tuna something. After enjoying a few bites, toss a bite under wherever. Make a trail leading to you, kind of like training a squirrel to eat out of your hand! Good luck. Cooked chicken and turkey are winners too! or a stinky can of mackerel if you aren't hungry!