Like Al said, cutting & splitting will get it ready a lot faster.
As for how dry it should be, I would think 15% should be dry enough for smoking. IMO
Construction Grade lumber is usually taken to about 20% moisture content.
Cabinet grade hardwoods in PA are usually Kiln Dried to 6% moisture content, and then steamed back up to about 8% MC.
As for air drying, unless you take the wood in your house, depending on where you live, it won't be easy to get it much lower than 15%, because it depends on the "EMC" (Equilibrium Moisture Content) in your area.
You can't air dry your wood to a lower moisture content than the moisture content in the surrounding air.
Depending on the time of year:
PA runs between 11% and 13%.
LA runs between 14% and 15%.
CA runs between 12% and 15%
In some states, such as Arizona & Nevada, the EMC is below 10%.
Link:
http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr117.pdf
My 2¢
Bear
Dewetha---You posted that while I was rounding up my numbers (took me awhile)---Pretty much the same info.