How Do I Make My Mares Mane Thicker?

My mare's mane was thick during the warm weather last year and then during winter it was cold where I live so I always kept a blanket and sleazy on her because I didn't want her to fuzz up because I show her. I am wondering if the sleazy rubbed it some although I didn't see any mane hair on it. I asked my vet and he said put her on nu-image a supplement that helps hair growth and helps the hair coat get a show ready look. I have nocited that it does do what it says although it is helping her mane it is kind of slow but it helped her coat in no time. But it is working, I have heard of MTG and do use it on her tail. What are some quicker ways of getting her mane thicker? Also any other advice?