I use mostly dry yeast, but I never add it directly. For my 1st batch, I followed the hydration instructions from Palmer
. For my batches now, I hydrate well in advance (4 hours or so) with cooled boiled DME and water, and let the yeast get going a little. I normally have action within 6 hours. For the times that I use liquid, I always do a full starter a couple days in advance. I also normally pitch 2 packets of dry, as opposed to 1. Costs a little more, but I have never had an issue with lack of fermentation.