One way to use OG is to use the Quant and Verbal Reviews as practice problems with the MGMAT books
and to save OG12
I've read that some people suggest doing OG12
problems in sets of 37 Quant and 41 Verbal problems to replicate the test-taking experience.
Regarding Accuracy/Speed, I think you should only do OG problems timed. If you need longer than the alloted 2 min./math or 1.75 min./verbal, take the time to accurately complete the problem, but count the problem as "Slow" so you can be sure to take the time to review it once you finish your problem set.