Nope, they won't.

But their tiny crawlers (newly hatch young) will still be on the plant.

I'd like to know what variety of plant it is and maybe even see a picture of the pest. Jean is right, but having further information will be helpful in looking into your future.

Hard to answer the general question specifically. There are hard-shell and soft scale types. Hand-scrubbing may not be as thorough as a soft bristle-brush scrub. You are in zone 6, so there would likely not be much winter movement, either on the plant or from the ground.