Full strength white vinegar on carpets and diluted Pinesol on walls and floors works well. Unless you are a breeder of cats it is best to have your cats spayed and neutered at the youngest age possible to stop the instinctive spraying behaviour and it helps to stop the attraction of non-neutered outdoor visitors.
I used to get tom cats spraying on my front verandah (I had my own cats inside). I threw hot water with disinfectant in it all over the verandah - I used quite a bit but eventually the smell went and the cat/s never came back - don't use bleach as that attracts more than repels. I can't remember what disinfectant I used but sometimes I'd put a whole bottle of disinfectant into a bucketful. l You could try lavendar or maybe apple scented disinfectant
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