Assuming you have ID'd these pests correctly, they are not harmful to either the azaleas or the boxwood so you really don't need to do anything. If the pests are bothersome to you, then just spray down the plants with water to discourage them.

btw, there are very few insecticides that can be applied to repel or ward off/prevent insect problems. Most are either contact insecticides - the target insect must be present and alive when spraying - or the insect must eat recently treated foliage.

The most important thing is to correctly identify exactly what the insect pest is, if it is in fact a problem and how and when to best treat it before you spray anything.

I use Permethrin. Love the stuff.