I use Lincoln's Menthol and Camphor cooling gel. However I believe it is banned from Racing but not BSJA, BE or BD. I find it brilliant stuff and lasts for ages.
I've just bought a bit tub of the equine america one, seemed to do a good job, I put it on after he'd had his cool boots on. You do need to be careful which one you choose as there are a lot that are not to be used under 'rules', think its the camphor, but could be wrong