The search for the missing votes

Candidates Head To D.C. As Florida Audits Votes has this regarding the race with the missing 18,000 votes in Katherine Harris' old district:

The audit of Sarasota County's 13th District race will include ballot accounting, tabulator performance and forensic analysis, Secretary of State Sue Cobb said in a letter to Sarasota County Supervisor of Elections Kathy Dent.

Officials will also conduct at least two "parallel tests" of the voting equipment, using four of the spare machines that were not used on election day.

What are the nuts and bolts of how these will be done? Please let me know in the comments.