I have the big Andis Progress clippers and they have never failed me. They are the best clippers Ive ever used and give a professional looking cut. Theyre well worth the money
I use K2 clippers and they're great, and they don't even get ridiculously hot! for a very thick coat make sure it's super super clean, showsheen the absolute life out of it and allow it to dry before you clip, it'll help
Liveryman harmony plus clippers are amazing on all types of coats 👍🏼
Double K!! Only clippers I will ever own. They are expensive but so worth it, I got mine used 10 years ago and still going strong (I do get them serviced every few years). I use them on everything tho, my Morgan, my wolly mammoth Minis in the spring, I've even shaved a dog with them and an extremely matted cat that showed up one day.
I really like the lister star Clippers! Or lister legends
I've used Oster's Clipmaster body clippers on my guy who has a very thick coat with a good bit of success.
Cow or sheep sheers may be your best bet, then go over it with a finer set of horse clippers