Trenching is a bugger.
Are you going to reuse the native soil after ammending it or are you going to haul back out and replace with another "topsoil". I generally use the native and ammend but either way it involves wheel barrows and a lot of work. Putting tarps down with lots of bricks to hold them down helps with clean up. Testing soil, including "topsoil" products ahead of time can tell you what else may or may not be needed. You may have picked up on my displeasure with screened manufactured soil, they lack structure/aggregates and you wont know what chemistry is going on unless you test it. They can take subsoil, blend it with enough compost and it will look and smell like rich good topsoil but is actually crap. Having a good and trusted soil and ammendment source could change that I suppose. We deal with different soils than you folks.
As far as innoculants, I'm more of a mulch it/compost it extensively and improve conditions for the soil organisms already there. I once brought in some forest soil for a beech tree project I had once however. I will also use a compost extract for soil injection as well but no commercial innoculants.
