I have a IEP and then what?

You cannot do everything by yourself in a classroom to assist a student with ASD. You have to work with his strengths to improve his weaknesses, they  are your allies.

 If he is  non-verbal, but has a good visual memory: insert pictos in  a routine.

Lacks social skills, but likes computers: give him the chance to pair up with someone who is less efficient or rather someone who shares the same interest. 

He is rigid, but laughs easily: enter your new concept like a game.

 If you persist on working only on his  weaknesses without knowing or recognizing his strengths, your plan of action is doomed to failure. If someone asked you to work on something really hard for five hours per day without having  a certain satisfaction, you would  probably be frustrated. 

"Practice makes perfect" applies when you have an interest or skills. If it's always done the same way, it just proves that you are not very flexible yourself. If you really want your student to improve and acquire certain skills, you should try different approaches. If your student with ASD sees no advantage to do what you ask him, he will not do it, period.