No thermometer it wont help. For a coil 10ft is fine but it looks long when you buy it but once you coil it you will see how short it is.
What you need is 1 foot of copper cut in half into 2 6″ pieces and run a water pump with 2 hoses. Water pump is like $4.
Ex shiner, pro cop troller, I can teach you how it is done if you don’t understand.