When we milk train our baristas at Hot Numbers we first use a barista thermometer. These thermometers are quick to react to milk temperatures which lessen the chances of overshooting your target temperature during milk steaming and burning the milk.
Features a stainless steel probe, protective sheath and a stainless clip for easy attachment to the milk jug. More importantly a green target temperature zone is indicated on the dial with which to aim for the ideal milk temperature of between 60-70 degrees Celsius. Once this temperature has been learnt through repetition, a competent barista should negate the need to use a thermometer and rely on his/her skill set.
A very handy and affordable training aid that we use on every induction latte art course we run at the roastery. We must also point out that it is useful for professionals to double check their temperatures are hitting the sweet spot every now and again!