I tend to be WAY too shy to ask a guy out, but if I have an "excuse" I go with it. (Keep in mind I'm single so take this advice as just one gal's opinion that may not be worth much.)
I would tell him I was stuck with some ASL thing, and would he be willing to help me. Then we'd go meet somewhere, start to small talk, and maybe eventually get to helping with the project! You know Deaf people can carry on small talk for HOURS! Then at the end I would be sure to mention that I REALLY enjoyed chatting (emphasis on that) and thanks for the help. If I were feeling bold, I would suggest we should go get coffee/drinks/whatever again sometime. Y'know really casual, but leaving the door WIDE open for him.