I used Clubman talc last week, when I had to wear a suit and tie in 90-F weather. It made a difference. Since I was traveling, I half-filled a clean sock with the talc and put it into a ziploc sandwich bag. To apply, just pull the sock out of the bag and pass it over your skin - anywhere you expect to sweat.
In Thailand I've seen mentholated talc for sale. That could be nice for 95-F and 95% humidity.