You will struggle with trimmers for thick feathers, you would be far better off with a set of clippers. There are I think andis trimmers that are very good but they are over £200 a set
My mare doesn't have thick feather, only light feather and I use the Liveryman element trimmers for her legs with the 3mm blade attached so they look natural.
I thought if i used clippers it would look as though I had, rather than trimmers which I thought may grade it in better! any ideas??
I think as Lizness says, you'd be hard pushed to get through the hair, my lad has short but dense leg feather & trimmers wouldn;t go near it. I#ve mearly had to practise with the clippers to be subtle- I have Liveryman arena plus.
I have in the past had to remove the clydesdales feather for xrays and first removed all the long hair with sissors and then used clippers. If you want to blend in, take the clippers carefully down the legs in the direction of the hair.
You might get away with using the livery element clippers once you have clipped out, but having used them on a welsh C which had far less than a clydie or gypsy cob, they did do the job but I think would have struggled with a true heavy haired type. Again I removed the worst of the hair with sissors before using the trimmer.
I can say for sure that the very small trimmers won't even touch the hair, but the elements are fairly tough trimmers - I use them to tidy up beards, ears and have as said, done legs on a lighter haired breed.