Bandana on the head helps, sometimes a wet one around the neck does too. Used to be able to get cloth tubes full of hydrocellulose to soak and wear around the neck, they worked real good, but I never found wet stuff on my neck to be comfortable. A good product now is Under Armor, like sports pros wear. Just remember, its nylon, so it'll burn. I kept a big insulated mug handy with ice tea or ice water, drinking periodically while I worked. and such things as pickles are great for afterwards, when you really need the salt. And as far as that goes, if you've never had a nice cold slice of cantaloupe right after a hot session at the forge, you just don't know what you've missed. Mainly, though, learn to recognise the signs of overheating, and just quit.
Joseff