Cement mixer or 55 gal drum. Put the mix in the drum and roll it around.

Using a majority bulk compost then mixing modest amounts of the rest so there is some variety should work just fine. My beds were originally majority aged mushroom compost, and then I have added various purchased and homemade compost on top of that and raked them in to mix the top few inches.

For the few additional materials I did mix in at first, i would partly fill the bed in layers and mix a bit in place every now and then.

As suggested in Mel's second book, My wife and I used a large cheap plastic tarp (about 25x15) to mix the ingrediants. On a calm day (wind will blow the tarp around) we started with mixing the composts first by pouring a line of each compost down the middle of the tarp from 5 gallon buckets (6 buckets equal 4 cubic feet) then pulled the ends of the tarp back and forth a bunch of times until it was mixed. Then we added the 4 cubic feet of vermiculite and the 2 cubic feet of compressed peat moss (which we loosened up in buckets to get the 4 cubic feet uncompressed) and poured these onto the tarp and then pulled the ends of the tarp back and forth again until everthing was mixed. We dragged the tarp closer to the garden and then used the 5 gallon buckets as shovels and scooped it into the (empty) raised garden bed. Every inch or two we put down, we wetted it thoroughly. When the tarp was almost empty, We just lifted it up and slid the rest of the mix into the garden.