After watching some videos on Youtube I bought some small neodymium cube magnets for uncoupling my trains. I found that they were very strong magnets and were difficult to place between the ties/sleepers. After trial and error they now work well, are cheap, and are hidden below the ballast. It is important to get the north pole (red line) facing UP near one rail and the north pole facing DOWN near the other rail. I hope this will be helpful.