I've used a duct tape boot for years now, my veterinarian in Va showed me how
to make one for the very first abcess I had to deal with. They are NOT
totally waterproof, although they help. He had me make mine at least four
layers thick. I've never been able to get one to look anywhere near as nice
as the one shown, it looks like perhaps it is only one or two layer thick,
which will wear thru at the toe in a heartbeat unless you have incredibly
soft footing. I've also found that you really need to use the more expensive
duct tape, anything else is a pain (3m ANSI standard rated, the others arn't
ANSI rated, they're a pain).

When I've used the styrofoam, I used elasticon, taped all the way up over
pastern so that she couldn't walk out of the styrofoam. This is how the vet
did it, he cautions to not get a lot of pressure on the coronet band. On
soft ground it will last pretty well. When the ground was harder, and she
was wearing right thru it, I used a duct tape boot on the styrofoam only,
then elasticoned the entire thing on.

You can buy elasticon fairly easily thru a medical supply store... find them
in the phone book... call to be sure they carry it in at least the 3"
version. I last got a box of 6 in the 4" width, for $45 + tax. Much cheaper
than the 3" from my vet (2 for $20), and no need to wait for shipping.