We have the Technique Hyperkewl evaporative vests. Soak in water for 2 - 3 minutes, then gently wring it out. I towel off the inner liner. It is damp, and will get your shirt a bit damp, and if you have a backrest it will get that wet. I used a plastic bag on the backrest, but the vest does not drip unless you leave it loaded with water. The cooling lasts from gas stop to gas stop - Gloria thought it stopped cooling, but she just got used to the coolness. She put her hand against her skin and found it much cooler than her skin not under the vest. (I put a thermometer under her shirt by her shoulder undwer the vest and it was 16° cooler than the air at 103°)
BTW - that link is very informative, but Widder went out of business in 2009.