In our raised bed garden, we use a growing mixture (not really “soil”) made up of several components, so they must be thoroughly mixed before adding to the garden. Since we’re dealing with a couple hundred pounds in each batch, mixing take a bit of planning. Here’s how we do it:
As the rest of the components are added, one at a time, the flat side of an iron rake is used to mix it well before the next component is added. It should be pretty well mixed before the next step of rolling it in the tarp.
I use a large grain shovel to move the mixture into the raised bed. A 2×4 is dragged across the top to level it out.
Don’t plan on doing more than a couple of batches a day – it takes longer than you might think to do a batch, and it’s pretty heavy work.