No offense for me. This is a problem archaeologists have to navigate as well. Digging is destructive, but it's the means to arriving at the truth. Work is meticulous and slow. Look how tidy those holes are! Typical tools might be trowels (like cement trowels and with straight edges, not like garden tools), a little whisk broom, even toothbrushes. The dirt from the dig spot is put through a gigantic sieve by the bucket load, so that artifacts that aren't picked up by human eyes show up on the top side of the sieve.
Digging is layer by layer, little by little, not 6 feet at once!
It's likely LE has additional ways to narrow the spot to dig. Note in the photo, they've dug a hole in the shape of a rorshach blob. That's pretty specific.
One of the bigger surprises to me in this dig operation is that LE hasn't gridded out the search area. It's possible they do that electronically, I suppose.