I have a mare that has an extremely thick mane, and every time I try to pull it, she throws her head. She didn't always do this; she just picked up this behavior last summer. Any tips?

My gelding has an INSANELY thick mane and will never stand to get his mane pulled. Not because he is badly trained, he's just VERY fidgety. I saw this "Solo Comb Mane Thinner" here: Solo Comb Mane Thinner - Grooming Products and thought it would be a fix to my problems. My parents don't fund...