Hot clothing - make up a bucket of water as hot as you can stand and add a splash of white vinegar or dettol - some use baby oil but I find this makes the grease worse - and rub the wrung out cloth all over the horse.
Yep, hot clothing! Water as hot as you can stand, dash of White vinegar, cotton towel wrung right out and wipe over.
On a show day do this, then do it again but add a dash of baby oil or pig oil (literally just a dash) as it will give an amazing shine! Though this does then risk picking up dust soots just a last minute before a comp wipe over.