We bought our irons from L&H. They are good people. The brand blurs when the hair grows. If the hair is very long, as it grows it lays over the branded area. Smaller brands look best on short haired animals like a horse that has a fine hair coat. We branded a horse for a woman. Her brand incorporated a one inch capital H. When the horse's hair grew in, the bar of the H almost disappeared. It showed clearly when she had her horse body clipped.
This is our oldest daughter's brand (the rocking penguin). It will fit inside a 4 x 4 square. You can sort of see how it distorted when the horse's hair grew back in.
2 weeks after branding:

several months after branding:

Horses require less time than cattle because they have a thinner skin. We used a twitch without any problems, except there have been some horses that are difficult to twitch. They were tranquilized.
Something else that you may not be aware of, is that when you brand a young animal, the brand grows with it. So if you use a large brand like yours on a weanling or yearling, it is going to be huge when the animal is grown. The largest size that we will use on a horse is 4 by 4 inches, and will only brand horses 2 years or older.
This is a good publication about freeze branding horses:
http://animalscience.tamu.edu/files/201 ... orses7.pdf