If you or one of your students wants extra pronunciation practice then try using Google Voice (GV) at home. Google Voice works on any mobile device and is very accurate with native speakers. You can focus in on some pronunciation issues and GV will tell you exactly how you are pronouncing something. Practice saying the word until GV dictates the word you want to say. For example,
You want to say, “wait a minute.” But, GV is dictating “white a minute.” So, practice saying “wait” until GV dictates it and adjust your mouth formation accordingly.
You can do this is the privacy of your own home and test out all types of crazy mouth/tongue formations without the eyes of your fellow students on you. Try it in class later to confirm accuracy. But, if GV can dictate it then you are speaking like a native English speaker. You can adjust the language to British or American English, depending on the accent you are studying.