Unfortunately, people will interpret your comments according to their own biases, and I've that a lot of people are biased to distrust or dislike introverts. For this reason, I would never admit to being an introvert, in a business setting. I would rather tell people that I'm mildly extroverted, and then let them believe what they want.
Some hire an MBTI consultant for whole workshop days. Some just order a pre-made test.
"I have to be alone very often. I'd be quite happy if I spent from Saturday night until Monday morning alone in my apartment. That's how I refuel."
[edit] to clarify to whom I'm agreeing.
No psychologist worth their salt would define an introvert that way.
http://www.dictionary.com/browse/introvert says:
"introvert
noun
1. a shy person.
2. Psychology. a person characterized by concern primarily with his or her own thoughts and feelings (opposed to extrovert ). "
Get enough private time and rest before you speak, and after if you feel tired then.
Introvert != shy
Introvert != stage fright
Introvert to me simply means I have a shorter energy supply when around people I don't know.
The closer they are to me, the more I can be around them without getting tired.
So don't equate introversion with social anxiety or inability to speak in public.
So with that said, learning public speaking for introverts should follow the same rules as for anyone else.