This little jig will let you enter RCM mode without having to sacrifice a Joy-Con or hold a piece of wire. You will need to break up a Micro USB connector to get at the pin contact wafer inside, remove all but pins 1 and 4 (which will contact pins 7 and 10 on the Switch respectively), short them together at the rear, then insert the wafer into the 3D printed jig. Trim it to fit and superglue it in place, then verify that the placement looks good.