It’s essentially a black, water based epoxy that conducts low voltage electricity when dry. I’ve used it on wire-to-wire connections as well as on rail joiners without any problems on my N scale layout. I put a little dab on the rail joiner and it flows right into the joiner. Slide the track ends into place and let it dry, which takes about two hours. Because it’s an epoxy, it creates a strong physical bond so it seems to have all the benefits of a soldered joint with out the hassles.
One caution is that I don’t know if it is incompatible with DCC applications since I am using block control on my layout but it might be worth setting up a DCC test track and see if any problems arise.
A 0.3 fluid ounce jar costs about $5 (plus shipping) and can be found on the manufacturer’s website, www.andersproducts.com, or on EBay.