TNR is not actually better than trapping and euthanasia for reducing cat populations. That's mostly just pushed by feral cat advocates based on misinterpretation of a couple studies. Those same cat advocates tend to be much more helpful with giving information on how to shelter and feed feral cats than how to actually get any of the cats fixed. Trapping and euthanasia of feral cats is generally thought to be far more effective and cheaper, but it's unpopular.
https://www.ncbi.nlm.nih.gov/pubmed/23009077