I have been using Red Star Instant Active Dry Yeast for about a year now
and I think it is JUST WONDERFUL. I buy it from King Arthur Flour. It is
supposedly a little different than instant yeast, according to the catalog,
but similar. You add it directly to the dry ingredients. The package says
not to rehydrate the yeast before using it. I have used this yeast for
pizza dough, bread, bagels, soft pretzels and doughs that start with a
sponge and it works great for everything. I keep it in the fridge and then
just take out what I need, sometimes I let it come to room temp. if I have
time, other times not. I can't remember if I have used it for sourdough
bread, but I never have luck with sourdough bread. If I did use if for
sourdough and it wasn't that great, it might not have been due to the yeast.
Kathy