It is not really very hard to bath your horse but some small tips can make it enjoying for both of you and easier for you.
1. Brushing the horse before the bath is a good idea as it will help him get rid of extra dirt and hair.
2. A bath should start from the leg and moving up-ward is a better idea than throwing the water from top and then washing the horse.
3. You can use a little warm water, around 100F, for the bathe.
4. If it is summer time, you can use normal water or a little cold water for the horse.
5. You should take care of safety of your horse as bathing is a time when many safety precautions are on hold.
6. After the bath, make sure that the horse is fully dry before you let him go.