I was given a bottle of Feliway, and was told to spray it on the cat. But the Feliway website says do not spray it on the cat.
First I sprayed it on my hands (because I was afraid spraying on the fearful cat would scare her). Then I pet the cats. Garfield became so affectionate he almost made me crazy. He is always loving, but it was like he couldn't stand to not be touching me and rubbing me continually. Jill, the semi-feral girl, just seemed to calm down, and begin to feel more comfortable.
I continued to spray the "cat chair" where the cats love to nap. I would spray a towel, and lock Jill in the bathroom by feeding her snacks, and slowly catch her with the feliway towel, hold her securely, and pet her for about 10-15 minutes so she could learn that sitting on laps was enjoyable.
And I would spritz it around the house sometimes. It is supposed to be the hormone from a cats chin, that they rub on things they mark as their own. So the smell gives them a kitty message saying "its safe here" "you are comfortable here".
Try spraying some usual cat resting areas, so each cat will get the hormonal message. Spray daily, or several times daily. Soon you will probably see them relaxing, and forgetting to hiss so much!