In our slatted cattle barn which is fully confined with no added outside water this is how we handle the manure. Each pit in our barn holds about 700,000 gallons which is applied via custom dragline.
(1) we add about 40,000 gallons of manure from an undersized outside pit in July to each pit. This is about 1.5% solids
(2) the day before we are to pump we agitate the next days pits for 2.5 hours each with two 8" Nuhn pumps and one 12" Nuhn pump. This gets it 80% stirred, not ready to pump but close.
(3) the day we pump we put the three pumps back in for an hour before we take anything out. Then we start to load with the 12" filling tankers, and the two 8" pumps moving around to different locations in the pit, where they 
continue stirring until the pit is about half empty. Then those two pumps move forward to the next pit to start on the final stirring in that pit, where they will have about two hours of pumping before the load pump gets there.
When the load pump gets there it can start loading and keep the trucks and dragline moving.
(4) We test the manure each year and are pumping 11 - 11.5% solids from the top to the bottom of the pit.

We have no experience with less solids and  how it might settle out but thick manure stays in solution pretty well.