For the most part they all work and offer improvements but they should be used accordingly. Using SST or SilClear for example on interconnects, power cords, speaker wire etc that are of an all Copper configuration doesn’t make a lot of sense to me as I don't believe in bringing in a new element to the contact surface only when Silver isn’t being used in part or in whole as a conductor. If Silver is being used it becomes a different story.
Many years ago Sovtek came out with a limited run of contact enhancer that was about the best that I have seen. Problem is they only did it for a few months and then it was gone. I picked up a case and use it sparingly now on one of my power cords in conjunction with some enhancer I had custom made. I should mention however that I don’t do it to improve sound or anything along those lines, I use it to increase current flow and to protect certain areas of the cord from possible contamination years down the road which is in all honesty what its intended to do. If a contact enhancer claims to do more then that (better bass, lower noise floor etc etc), I want no part of it.
Anyway, if you want what I consider to be the best all around contact enhancer for general use, stick with Caig as it does what its supposed to do and it will stand the test of time with no adverse effects years down the road. If you want a free tweak, warm up whatever you are going to treat for a couple of seconds and then apply whatever Caig product you are using, let it cool and apply again at room temperature. Please note I said warm it up, not heat it up! Just make sure you can live with the results as there is no turning back. Once done there will be traces present on the contact points 5 years from now.