While alu foil is a good conductor, faced with the risk of exactly that getting loose inside your Switch wihtout easily getting it out - dont do it.
If just a cable touching the fan (housing?) on one side, and pin 10 on the other side does it - it realy doesnt get much simpler. For "daily use" hopefuly some 1USD trinket will be available eventually, if this turns out to be the "easiest" way for most people.
edit: For people not reading the links, the github link above includes a 3D model of a plastic part that will fit into the rail, and instructions how to modify a micro usb connector and merge it with the 3D print to short two of the pins.
Thats an easy way you can make this "yourself" - if or some reason you don't want to just go with a cable.
And again - as soon as it turns out, that this is the method most people will be using, stores will be full of this "item".