As another, who sweats a fair bit during training;
I shower before I even go onto the mat, to ensure that, as 'gross' as my sweating may be, I am ultimately, not sweating or leaving anything unnatural behind.
I'll dry my arms on the inside of my gi, before a technique to minimise the chances of someone slipping off my wrists, and all, but the way I see it is that if people aren't sweating or looking flustered, then.. they're not putting enough effort into it..
We don't mean to sweat so much, you know. It's just a little hard to control