Rehydrating yeast questions.

Safale s-04 instructions.
Re-hydrate the dry yeast into yeast cream in a stirred vessel prior to pitching. Sprinkle the dry yeast in 10 times its own weight of sterile water or wort at 27C ± 3C. Once the expected weight of dry yeast is reconstituted into cream by this method (this takes about 15 to 30 minutes), maintain a gentle stirring for another 30 minutes. Then pitch the resultant cream into the fermentation vessel.

1. Do I need to cool the rehydrated yeast to wort temp before pitching?

2. How do I know what 10 times its own weight is? Or, is one cup of water fine for rehydrating.

3. Do I stir for 30 minutes straight?

boil 2-3 cups of water for a minute or so. Wait till the water cools to <80 f. Stir it around once in a while until all the dry yeast is dissolved in the water. You can also pitch it directly(dry) into your wort when your wort has cooled down to this temperature. No need for a starter. Just mix it around for a while since you have to aerate your wort anyways. You dont have to stand there stirring for 30 minutes.

I got is from another thread, posted by an expert in dry yeast. I have been doing this with S04 and works all the time:

Boil 2.5 cups of tap water (not distilled, not filtered) fort 5 min, cool to 105F, yes, 105F, dump yeast and wisk for 2min max, not 30min.
Cool further to 75F (pitching temp) and pitch to wort.

The high re-hydration temp is important to help the yeast cells to rebuild the cell walls. Not using sugar or any other sweet ingredient is also important.

Wow, I guess there's many ways to do it, here's my method:

Boil 1 cup tap water for a minute or two, pour into a sanitized vessel (I use a Pyrex measuring cup). Cover with Sarane Wrap and let cool to 95-105 F. Sprinkle the yeast and let sit for 15 minutes WITHOUT STIRRING. After the 15 minutes, stir up the yeast to thoroughly mix the solution and pitch into wort (assuming wort is already at pitching temp).

The dry yeast have been through a lot and you need to be real nice to them as they're coming back to life. They can't control what's passing along and through their membrane wall during rehydration. Abusing the yeast as you rehydrate can kill yeast and you may not get the amount of healthy yeast you desire in your beer.