Well first thing you have to keep in mind is they can only DI away in the direction you shined them. They will go left if you hit them with the left half of your shine, and they will go right if you hit them with the right half. Keeping that in mind, as soon as you shine them, look at which side of your shine you hit them with, then WD out of the shine in that direction. If they DI away from you, you simply dash out of the WD and you can jump into another dair shine, you can use some other aerial, or you can stay grounded and do something else. If they DI in towards you, they should still be close enough to hit as long as you waveshined in the correct direction. Just practice it vs. a level 1 Captain Falcon on FD and you should get the basic version of it down in no time. Then you can start adding little variations to implement more options like ending the combo with nair/fair -> fsmash or using falling single hit uair -> utilt.