I spin my cases with a battery operated drill in the flame of a single propane torch. Used Tempil to figure out how many seconds to spin case shoulder in the flame. Then I just place a clock with a second hand in the background and leave case shoulder in flame for the predetermined amount of time. The case head is held in the drill bit securely with a Lee case head holder w/adapter. When I remove the shoulder from the propane flame I continue to rotate the casing and touch the shoulder area down on top of a wet sponge that's situated in a convenient location for several seconds. The case will hiss like a hot iron and then cool very quickly to the point I can remove it from the Lee case head holder and place in on the table. Just keep the sponge well wetted with water. Whoever told you it's important to dunk the cases in water of the same temperature is full of it. The rate of cooling has little to no affect on the annealing of the brass. The time at your flame temperature is the critical part, which is what the Tempil helps determine. Too cool / too little time in the heat = no annealing. Too hot / too long in the flame = overannealed. There's some forgiveness in the proper heat/time zone.
In my propane torch with the flame set about 5/8" to 3/4" long, it requires about 5 1/2 - 5 3/4 seconds for .300 Win Mag size cases. Less time for .223. A little more for .375 Weatherby. Across all cartridge extremes the time in the flame varies from 5 - 6.5 seconds. I only used the Tempil to figure out the proper length of time in my propane torch flame. I basically never use the Tempil any more, as I now know about how many seconds in the flame is required for the various case sizes I anneal.
I've never thought it was all that easy to observe the Tempil melt. Others must have more calibrated eyes than I do. I've always found it tough to ID the very moment it melts / changes color. I'm probably spinning my case necks faster than the automated annealing machines, which makes it more difficult to observe the instant the Tempil melts. Good luck with it.
I just checked my Tempil and I purchased the 650F.