I like the one with digital display, but just because I'm lazy that way. I probably can't read a real clock dial anymore. Set to resistance (the capital omega symbol). Touch one probe to the hot lead (at pickup to switch connection, or switch to jack connection). Touch the other probe to a ground wire, or back of pot...any part of the circuit that is grounded. If the reading is zero, or near zero, then this is a short. You want to see "1", which is infinite resistance as there is no connection between your hot connection and ground. I recently had to disassemble a circuit because of a short. I checked for shorts as I reconnected all the pieces. As soon as I wired in my volume pot, it shorted. I found the problem soon after. Because it seems like your short is intermittent, tho, the multimeter may not catch it.