"Will it be possible for my female to ever get a breed survey since she never received an SG before 24 months of age? What kind of hoops am I going to have to jump through for this?"
To get a breed survey, the dog must have a show rating, IPO1 (or equivalent), an AD, Elbows certified by the SV, and hips certified by the SV or OFA. Now that she is over 24 months, she will have to get a working title like IPO1 in order to get a show rating. You can do the AD at any time with her.
"At what age do you start training your dogs for the AD and what's the best way to start?"
I cant really answer the first part, since the dogs I am training for the AD are over 3 years old. But our first bike distance was around 5 miles, and the dogs seemed like they still had energy after. This website may be a good start for you on how to train for the AD: