Any pest problem on an Indian Rope Hoya is hard to control because of those tight leaves. Use Insecticidal Soap or alcohol in a spray bottle, spray it thoroughly and rinse well.
Then add something with Dinotefuran in it (I use Ortho Tree and Shrub Insect Control Granules). Dinotefuran is a systemic (so if you have munchy kitties, don't use it) and the ONLY pesticide that will kill scale type insects.