Nice old thread.
...For radials I found when the yard was muddy it was fairly fast and easy to use a real large flat blade screwdriver to poke the wire a few inches into the ground and then put down a metal turf staple every foot or two...
perhaps the easiest way to do it is to use a sidewalk gas powered edge trimmer.
just walk it BACKWARDS and it will make a nice slit about 3 inches deep<More audio> drop in the wire and you're done.
I have 3 500 foot rolls of wire under mine