The Tempilstiks work much better if you heat the case a couple of seconds before applying them. You can also grind them up and mix a slurry with alcohol to dot onto a cold case, as one member did, but you might as well buy the liquid form (
Tempilaq) then.
Dropping into water is not only supposed to keep the head from warming enough to start stress-relieving, but it's also supposed to stop grain growth, which weakens brass. But a board member who is a metallurgist points out that grain growth takes time, and he doesn't think the thin brass stays hot long enough after you remove the heat that to become a problem. Besides, if you don't get it too hot in the first place, grain growth never really begins to any significant degree.
If you want proof your heads are remaining strong, you can mark them with 250°C (482°F) Tempilstik or 246°C (475°F)Tempilaq just back of where you expect the annealing stain to stop on the shoulder. If it doesn't get hot enough to melt that, it's below beginning to stress-relieve the brass in that location. Set it down where you can see that lower temperature mark, and as long as it remains un-melted, you're good to go and don't need to quench.