Whether to cut into the hill and use that material as fill or truck in depends on what looks like will work best for your lot and what kind of quality the ground material is. Consider handling water running from uphill. For a shallow fill like that, we'd more often raise the site, rather than both cut & raise.
Once you make that decision, around here, you'd have to remove topsoil to get down to virgin mineral soil for code due to stability. As far as the method on how to compact, depends on the capacity of your compaction equipment. To properly compact, you had the idea right, compact well enough it can be considered virgin soil. The compaction equipment we had required no more than 10 inch lifts per time. That is, the compactor was only effective for a 10 inch depth. What you do is level out your fill that deep over the area with your tractor bucket or blade then go over it with the compactor. Place and level another lift of fill over what you just compacted, compact and repeat until you get to the elevation you're after. Be sure that the slope away from your building pad is plenty shallow for ease of getting up and maintaining around the building in the future. Once the building is complete, take the stockpiled topsoil that was removed and distribute over your slope so you can replant if desired.
A surveyor's/contractor's laser transit makes quick work of ensuring you're bringing your lifts up level and even. Bringing up the lifts isn't precision work, so just setting the receiver on the staff at a set point then raise or lower your staff until it beeps. Eyeball how far to the ground you are and compare to other areas. Once you're near your final elevation, set your receiver height so that the bottom of the staff is your intended elevation. As long as you don't move your laser transit or the receiver on the staff, you're golden. You don't need to go all out and do proper surveying as you're just doing relative comparisons, simply follow surveying ideas of consistent methodology.
Great post, you seem to understand the situation. I own a rotary laser level and it has been very helpful.
To be clear, this is a very shallow fill making a 60' long wedge. The slope is barely noticable, trucks don't roll in neautral. Kids on bikes don't know if they are riding uphill or downhill. The building is so long that the slight slope adds up though so I need to fill in such a way that the fill acts like native soil. There are pole shops documented on this site that needed more than 6' of fill in a low area, and nothing but a LGP dozer was used to complete the fill.
I believe I will use the method of stockpiling the fill off the pad and then spreading it over the pad in level lifts. I can rent a real vibratory roller to seriously compact the lifts. Hopefully all in one day. I'm expecting this to require about 200 CY of imported material.
I do believe that the bottom of the post supports the structure. This isn't pier or pile construction. In those methods, the friction of the earth acting on the sides of the pier provide the support. Those piers can go down 80 feet!. You won't get much any of that type of support acting on a 6x6 post in the top four feet of earth. Prepare your post hole bottom accordingly. The biggest reason for compaction of the post backfill is to provide lateral stability so you can't push the building over.
I actually like the geopier suggestion. I could dig out a series of 4 foot deep post holes and backfill with rock or concrete.
One of the best ideas is to wait. Give the fill, and the subgrade, time to settle under the weight of the new fill. This is not a bad idea either, and will likely be how it goes. I plan to pour the slab after the building is complete. This should allow time for settlement. If the floor is still settling then I will postpone concrete.
I'll be sure to make a gallery thread. I've got the pad cleared of junk now. Moved the chicken coop, the firepit, etc. Fill is lined up. The recent wet weather doesn't help but tomorrow is the first day of spring.
