I would spray the plants and media with the mix (1 part of 409 cleaner, 1 part of rubbing alcohol, and 3 parts of water). Make sure you spray both side of leaves. I have used this mix several times, and it doesn't harm the orchids. I would repeat the process 2-3 times on weekly schedule.
Speaking of scales, I have just got an order of ~20 catts today. Most of them are healthy, but 2 of them have scale problem. I will make the mix and spray them this weekend too.