leak repair tonic?

Has anyone used these self sealing compounds that are injected/sucked into the low side and repair small leaks? I'm doing a repair on a glass fronted open display on the evaporator coil, that someone previously has tried braze up a hole made by a knife but I don't think they did a pressure test after the repair. And in turn has a small leak where it has been brazed. The options I have are replacing the evaporator if I can get a like for like match, cutting out the damaged section of pipe pipe and replacing with a new peice with two couplers filed out to make them into slide couplings and then leave that peice to ice up more as it willl have no fins on it, use some metal putty to seal up the small leak, or use the self sealing tonic.

I just wondered if they are any good and does the repair last? The last time I did a repair like this I flared a small peice in with two couplers. But there wasn't a great deal of room to get in with the spanners, and the section iced up more than the rest of it for obvious reasons. The customer was satisfied though as I stressed this before doing the repair, and told him it would still keep his produce cool as the airflow from the evaporator over the produce would still be almost equal overall. So he wasn't suprised when there was a bigger chunk of ice on the repair, and he was happy that I saved him money by not having to fit a new evaporator. I think the metal putty works down to a very low temperature once its cured, but I have only ever used it on hydraulic and steam pipes, with regards to the high pressure associated with it, it worked a treat. So if anyone else can share their experiences with the tonic, it would be most helpful.