Another topic after you'll master mounts is PAIN :) As you probably know already: NO PAIN NO GAIN. And that will last for some time at least.
We will still refer to Emily's movie: http://www.youtube.com/watch?v=ZIGexyg_qTU
prev note. It might hurt your knees at the beginning but believe me - it will stop after some time :) If you can not handle pain it will be better if you will still hold hoop with your hands, it will make it easier and your knees even then will have opportunity to get use to it. Don't do it too many times, at the beginning it will hurt you a lot! Especially AFTER or DAY AFTER training!
You can practise seats without hands on hoop, it will help your balance, which on hoop is REALLY important.
Pain will go away after some trainings. Just remember to always have few days break after your first hoop trainings if you've never did it before!
Sweating: On aerial hoop you don't need Mighty Grip, or you need just a little
bit if your hands are really sweaty, but also in that case you may use
special gloves or wrap your hoop with cotton ribbon.