I was into speed and i have been desperate enough to do this.
There is 250 mg in the cotton. That is a pretty big dose. The best bet, if you are going to do it, is soak the cotton in orange juice or water with lemon juice to get rid of the horrible taste. Then you throw the cotton away. If you know how much liquid you had you can guesstimate the doseage.
This is used as a weight loss drug in Europe at doses of 25 mg i have heard so that gives you an idea. Other people will cut the piece of cotton down into 4 or 5 pieces and eat them but its bad for you to eat cotton it can mess up your digestive tract. Not to imply that taking drugs is GOOD for you, but cotton is not either.
Speedwise, its harsh. Its certainly not as pleasant as crystal meth, cocaine, or ADHD meds. But it is stronger than caffiene and it is speed. The comedown is sort of harsh.
I cant recommend it but i know how desperate a fiending speedfreak can be. This one has been terribly desperate at times, but thanks her lucky stars she has never got ahold of some of these new things like MDPV etc...apparently they are super, super addictive and that would NOT be good for this speedfreak. She is lucky to have gotten away from the dope at all.
Be safe and if you are going to do this start with a LOW dose.