I would try to do some practicing online:

http://www.justanswer.com/

Online Doctor, Urgent Care Online & Virtual Doctor | MeMD

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Don't necessarily complete the online query, just pretend and do the write-up until you can think about the problem as just a problem and can state it well, etc.? In other words, practice. Then you can look at your options: someone online/on-the-phone; the ARNP; someone local/new to you, a stranger; "waiting".