Step up practice

We have been practicing the step up practice with Mina, every day for the last week. We practice in a less familiar empty room, using a chair as a perch. She is doing really well, especially stepping up from hand to hand, even though she aims for the shoulders very often. However, we don't even have to say the word 'UP', as soon as we put our hand in front of her chest, she steps up immediately. The only problem remains, whenever we need to take her off the roof of the cage. If it was for her, she would spend her lifetime on the roof of the cage, without even going in the cage to eat or drink. I have heard of the cushion technique. How do you exactly go about it? I always manage to take her off the cage, after some time, however, Mina makes it evident that she doesn't want to leave the cage.

Thanks

Catherine