Every technique must be demonstrated on a willing opponent. No one can teach a specific technique when their partner knows what technique it is and tries to prevent that single technique from happening. Even on some instructional videos when the instructor asks the partner to give some resistance, it is "fake" resistance.
What you also need to define is what you mean by "resistance". Resistance by a skilled opponent is different than resistance by an unskilled opponent. Someone can attempt to counter your technique with pure strength while others can counter it with technique. Similarly, resistance by someone below your skill level is different than resistance by someone of the same skill level which may also be different from resistance from someone of a much higher skill level.
The problem you are having may be that your instructor is teaching techniques that are way beyond your skill level. To draw an analogy, he is teaching you to do back flips when you can barely walk. For example, before you learn "cool looking submissions", you need to learn how to put basic techniques in combination. You will have extreme difficulty handling resistance if you don't know how to do combinations as combinations teach you how to move around resistance.
I think you should look into getting my Ultimate Guard 1 and Guard 2. That should provide a pretty solid foundation in which you can add other things onto.