Teaching a horse to tie up shouldn't be a messy process and can be taught to them in a safe and relaxing manner. This method helps to teach a horse how to respond off pressure without feeling trapped or the need to pull back, which can lead to the injury of the horse and the development of bad habits in the future.
For horses who struggle to tie up, going back to these basics is recommended, however, if they continue to struggle I highly recommend having their poll checked by a chiropractor to make sure they aren't pulling back from pain.