FYI, a number of the large courses on our campus have started using a new system called Gradescope to help us grade short answer questions on exams and homeworks much more efficiently. In Chem 1a for example (~1300 students), we were able to get rid of MC (Scantron) questions entirely on exams (three midterms and a final). 

Their website (https://www.gradescope.com) has details on how the system works - it really is wonderful! I believe it's in public beta right now and is free to use.