The Microtrains couplings generally work well, I've got practice at setting them up so they will uncouple over a magnet (usually!), and the magnets have to the the right strength and position. They couple up easily and don't give unwanted uncoupling. However if you need to uncouple where there is no magnet - such as in a fiddle yard - they can be a right pain. OK, you can do it by lifting one item of stock, but that isn't always desirable. So I thought I'd make a tool to help.
I think you can buy a tool like this in the US, but it isn't hard to make. I started with some plastic sprue from a kit, about 2mm diameter and roughly round, I shaped one end to a square section then tapered to a point. To make a handle a couple of diameters of plastic tube were used, then in the other end I stuck a tiny round magnet - only because I had one, and it allows the tool to hang from a steel screw in a convenient place.
To use it is simply pushed in between the couplings from above then twisted, the square section pushes the couplings open and apart. With lighter stock such as these wagons it takes care not to derail them, but gentle finger pressure on the stock can ensure they stay firmly on the track. However it works rather well and proved useful at Shepton Mallet, in fact I might make another because I am bound to lose it!