Yes sweating does work. It can make a huge difference. I only sweat the neck and throatlatch never belly. I don't see how those belly sweats work? You need to excercise them before you can get any sweat going and by excercising them they loose that belly. We work them using an neoprane neck sweat with an sweating agent. Than we keep them in there stalls where its warm and keep the sweat on for like an 1hr. Anytime we don't work with them we have a fleece lined neck sweat on them the whole time, taken off daily however, and we always keep there throatlatch sweats on. You need to wash there necks like daily if you do this however.
The only horses we sweat would be the show horses no others.