Yes, if you have the line disconnected at both ends, you should be able to blow air through. I would check two things though. 1, make sure the lines are not swapped making it so you have the rear lines disconnected at one end and the front line at the other. 2, I see you have the nut backed off that holds the small hard line to the master cylinder off. That line being so short is quite rigid. Did removing the nut actually open a gap up or is the line still pressed hard into the master cylinder?