I did the AARP Tax-Aide one year. It is a similar program, with the same training and software. At that time = you must go through their training, regardless of how knowledgeable you are. You use their computers which are property of the IRS (if I remember correctly) and are directly filed with IRS. The hours were 10 to 2, which really gobbled up the whole day. It was upstairs in a an big room with probably a dozen preparers sitting in long tables with the clients across from them. Definitely a great program that really needs the volunteers. 

This is from their site https://www.irs.gov/individuals/irs-tax-volunteers IMHO - It is NOT a road to building a tax practice, if that is your goal. 

"Tax Preparer – You complete and successfully certify in tax law training, including the use of electronic filing software, to provide free tax return preparation for eligible taxpayers."