Yup, kmaproperties has hit on a good idea, you can change the soil bearing properties with various additives. Here in Ohio some sort of limestone is the product of choice. In New England it is granite dust. What is it in Florida????
So part of the problem is understanding what is the "Preferred Stuff" in your area. Did your buddy bring the nice stuff????? Or do you just have "Dirt" of a bastard quality????
Couple other tricks to getting compaction. We used to dig up sidewalks to get at the utilities underneath. Then of course needed to repour the sidewalk. To eliminate renting a compactor, I would use a garden hose and plenty of water on back fill in the trench which could be 6 feet deep to make a mud slurry. If all the dirt went back in the trench exactly at the same level as before it was dug, we had the same compactation. Actually could achieve it a couple of days with the right techniques. Then repour the sidewalk with no problem in future settling.
So if you have access to large amounts of water have get very nice compactations, even over large depths just by creating and containing a mud surry. In your case, the sticky wicket is large fills without treatment in layers, no matter your treatment method.
Today I sort of have your problem. Need dirt to fill a large depression in my planned parking area. Getting some sand / clay free from former flood debris, put it down and roll over it with the truck if dry. Compacts good in small layers, can still be a bear if rained on. Will eventually need a limestone gravel mix to make useable. ---- difficult to get "Dirt" here. Good gravel, still ain't found the "Right" source.
Soil mechanisms is an art, science and what do you have to work with. What you got??? Followed by how much does it cost and what can you do to influence the properites??? I need some large limestone gravels made for driveways, spread just so as cheap as possible. Truck charges are probably going to eat me alive. Locals are no help. Local concrete company wants $15 a ton for fine gravels. Mumble, Mumble.
So, it comes down to:
Treat in small layers
Get the "Right Stuff" for your area
Understand a bit about soil mechanics
Understand your time horizon and how much compactation do you expect from your present methods and techniques based on the soil types you are working with. Ask around the locals, should know the practical answers. It has all been done before.