Kevin,
I just use ivomec pour on and spray it over the days feed. Figure our how many pounds of deer are in the pen and use the recommend amount of ivomec pour on for the deer weight in the pen. I always use a little more, about 1/4 more. Let the grain air dry in the sun and I feed it the next day. It is well accepted by the deer.
I'm afraid most worms are resistant to most of the wormers we now use. Mostly due to our not using enough of the wormer product when we worm our deer. Any worms that survive the worming become immune to that wormer. So pretty soon all the worms in that deer don't get any effect from that wormer.