I too have mealybugs on occasion. Seems to happen more in summer and when the air isn't circulating enough. I have alcohol in a spray container and spray the leaves, stems with it. If I have blooms, I use alcohol with a q-tip. Takes alot of patience, but the orchids are worth it.
Something else I do when mealybugs or scale seem to be nesting under the medium is use a used up cigarette filter. I take the paper off the filter and stick the filter down into the medium. It acts as a natural insecticide. It stinks like the dickens, but okay once it's buried in the medium. The nicotene residue on the filter is the insecticide.
I mentioned this once before and got alot of negative feedback about it, but it worked very well for me several times. (Mention was of a tabacco (sp) virus)....but
I don't know, I found out about using this natural insecticide in an orchid book I have.
I certainly don't have a problem using this method over store bought chemicals. But that is just my choice.