Start Friday--football on Saturday--sow seed Sunday. I think it would work fine to add seed 48 hours in advance to a tank or hydroseeder tank to speed germination; (cold weather or bad conditions, it might be needed). I am sure you would want to bubble air through the slurry. And you would want mild agitation (maybe no air needed if good agitation). Seed contains chemicals that prevent premature seed germination. The chemicals are leached out by soaking the seed in water, and must be removed with aeration or by changing the water. How warm should the water be? How much air? How often to change water--if at all? Can it start 72 hours early? 96?
What works best? Rye? Blue? Fescue? Bermuda?
Naturally, you would add the wood fiber mulch just before applying the mixture.
I am sure this has been done and tested many times by the hydroseed people.
What about it, Turbo?
Good question--will customers pay more for pre-germination of the seed? Quick green, is it worth all the extra trouble to you as the contractor?