One week ago, I adopted a 1.5 year old male cat. He was neutered the day before I brought him home. The cat had been living outside and being fed by someone before being trapped at a private residence so he could be adopted.I currently have a 5-year-old neutered male cat, a 13-year-old spayed female cat, and a 5-year-old spayed lab mix. I have been doing a careful introduction of the new cat to our household.The new cat would initially run and hide in his tunnel when hearing someone approaching. But he would let us pet him at any time. He is extremely affectionate. Over the last week, he will now come out and stay out of his tunnel when I talk to him. He occasionally gets a little scared and will go back in the tunnel if someone comes upstairs too noisily.He has been in our bedroom only. I've taken him out several times, put him in his carrier, and let the other cats sniff the room. After a day, I hung a screen door at the bedroom so pets could see each other. I've fed all 3 cats on either sides of the screen door, and then allowed my other male cat in the room for increasing lengths of time for the two to get to know each other. Then they spent the night in the room the last two nights and are playing and chirping at each other (which is so fun to hear, though after two hours I said ok boys, party's over, and took my older male back out of the room). I’m working more on introducing the female cat now, who mostly stays downstairs.My question regards spraying. The first night, I put the litterbox in the adjoining bathroom, and showed him where it was. I believe he was too scared to venture to use it and he peed on the carpet in the bedroom. I cleaned using Nature's Miracle and moved box to the bedroom, and added a second litter box. Since then, he has used one of his two boxes every single time.I noticed during the 2nd, 3rd, and 4th days, the room would periodically smell terrible, worse than cat pee. I bought a black light and discovered he had sprayed the walls and doors on two sides of the room. I washed the markings with Rocco & Roxie and he hasn't sprayed since. This also was the same day my other male cat spent the night in the room and they seemed to become friends.It is my understanding that cats can spray from stress and habit. He has certainly been under enormous stress. Because he was not neutered until 1.5 years of age, I am concerned he might spray once allowed to explore the rest of the house, which I feel he is nearly ready for. I know I need to work more to transition him carefully to our dog because he seems stressed when she is on the other side of the screen door.Will cats spray the same areas repeatedly or move on to other areas? Could he spray again out of habit (though he has stopped so far)? If he feels happy and safe might he stop spraying? I understand that they can continue to spray even after neutering for several weeks to months.Any suggestions for how to keep up the no spraying would be appreciated. He has gone from 0 to 90 in adjusting in just 7 days; I want him to go the other 10 percent as comfortably for him as possible. He is an awesome cat. Thank you!!