For my first TNR, I trapped a feral mom about three months ago. Just two weeks after she got in the middle of trapping her kittens. I wasn't sure I could trap after that experience and it wasn't easy. But trapping Libby was successful.
She had to be at the mobile clinic at 7:30 so I was told to not feed or water after 10pm. I wasn't able to get a loaner trap and ended up trapping her in a borrowed parrot travel cage. Not an ideal situation. Plus the other two ferals kept going into the cage and eating the bait food. Finally, around 8pm we got the door slammed shut on just her and then moved her to the garage.
I put the cage onto newspaper and put a towel on top of the cage. When I checked on her 30 mins later, she had shredded the newspaper and towel. And she was really mad. I removed what was left of the towel. I checked on her every couple of hours and she was so mad that I was scared at times. She messed in the cage and it was a battle for me to try to clean out what I could.
The next morning she was a little calmer but so pitiful with the howling. Finally, when it was her turn at the mobile clinic, she scared the assistant so much that they told me I wouldn't have to wait until the regular 3pm pick up. They would call me as soon as she was ready. I picked her up at noon. She spent the rest of the day and night so groggy. I only went near the cage three or four times to make sure she was still alive.
I was supposed to turn her loose into the backyard at noon, but by 7am she was alert again and knew she was trapped. She had pulled another towel in the cage and shredded it. The howling was terrible so I let her out 30 mins early. Since it was July 4th and the neighborhood behind us sets off fireworks all day and for the next week after, I felt bad that she was still kind of doped up, but thought that the earlier in the day would be better than at dusk when the fireworks were just starting.
Earlier that morning, her older kitten, Grin, had caught a large lizard on the patio. After awhile the other feral, Todd, took it away from him. When I put Libby and the cage out on the patio, Todd was laying under the table with lizard. I waited ten minutes for her to figure out that she was in familiar territory before I opened the cage door. She darted out of the cage, slapped Todd, grabbed the lizard and ran off into the woods. I honestly felt that I would never see her again.
Two days later she was there in the morning to eat with Grin and Todd. Last week, nearly a year after she showed up on my patio, I put a treat into my hand and she licked all my fingers and then ate the treat. We do this once or twice a day now. So, she doesn't hate me that much anymore.
My suggestions are if you think after you trap that the cat is truly feral or really freaked, just put it in the dark and don't cover the cage with cloth. After I saw that Libby had shredded the towel, I worried that she must have ingested most of the material and that might interfere with her recovery. I almost didn't take her b/c I was worried about what she'd eaten. But I was more concerned that she'd get pregnant again or that I couldn't trap her again. So I took our chances and we got lucky.
I learned so much from this website. Also that everyone's experience (and every cat) is different. Just do the best that you can and you will do well. And after your first time, even if it doesn't go exactly as planned or textbook, it is very rewarding.
Good luck to you.