There are a lot of things you can do to make it easier for your horse during the shedding season. The main things to consider are balancing the diet and caring for the coat.

You can speed up the hair loss process, relieve itching and reduce the risk of diseases through daily thorough brushing. Good tools help. There are dedicated combs, scrapers and gloves of various kinds, more or less specialized for the different layers of fur. 

A healthy horse that receives a balanced diet of roughage sheds faster in the spring than a malnourished horse does.