The anti-spark needs to be the connection that closes the circuit. If you connect the batteries to the Y cable first, the circuit will still be open. Then when you connect the Y cable to the machine, that will close the circuit and create a rush of current. The Resistor in the QS-8 will slow down the rush of current and minimize the arcing. Note: you need to plug in the QS-8 slowly because the first few millimeters at the tip of the connector will run the power through the built in resistor, then when you seat the connector all the way it will bypass the resistor so that it doesn’t burn up durning operation.
With what I described above, the switch will need to remain on (or be removed), otherwise the switch will be the mechanism that closes the circuit and the arcing will occur inside the switch. So you need to either use the QS-8 instead of the switch or add a resistor to the switch. Here is a link to my solution back in the day.
Another option is a button the you press while activating the switch. Here is a link showing that idea. I recommend a 22ohm resistor instead of 100ohm as shown in this link: