When corn starch is added to icing sugar, has it been cooked

When making the slurry, stir cornstarch into cold water until it has the consistency of cream. This can be set aside until it's needed, but be sure to stir it briefly before you pour it into the sauce to redistribute the starch granules in the water. You should pour it into your sauce toward the end of its preparation.

According to McGee you should use roughly 2/3 as much starch as you would flour. If you aren't using a recipe, add your slurry a bit at time until it's a thick as you like it. Also remember that the sauce will thicken a bit as it cools, so it should be a little bit thinner on the stove than you intend to serve it.

It's the water in your skin more so than anything else that makes it stick to your hands; generally the most effective way to prevent any kind of water-based dough or batter from sticking to your hands is by greasing them. Some of the fat might get into the dough, but not really enough to make a difference.

Any kind of fat will do. Vegetable oil is the economical choice but margarine or shortening will coat the hands much more effectively.

If you've got gloves then it's even easier, just spray them generously with cooking spray before you put them on and start to work the dough.