Good advice here.........
I posted last winter about a foundation bred AQHA mare who wouldn't slow her trot to a jog. She had been to three different trainers with little success and I refused to ride her with a twisted wire snaffle and running martingale. A reply from Ireland suggested starting her all over again and using a french link snaffle. Another suggested stopping and backing her when she sped up, another suggested small circles etc.
The french link bit has been great! She's dropping her head and doing a nice, soft jog at last. I'm not asking for collection, just keeping a rein in each hand low by my hips and she's doing great! A major problem I had was leaning forward when she trotted too fast, making the problem worse.
Anyway, thanks for all your advice.....this is an awesome forum!