Now would be a great time to transplant a dogwood in a warmer area, but might be a little late in colder areas depending on when the ground will freeze at that location. It's best to have at least a month between when you transplant and when the ground will freeze.

Don't prune until dormancy (early spring before bud break would be best). Cutting back hard when transplanting (before dormancy) would increase stress.

Why do you want to prune them, anyway? If they are tree-form, then no pruning, other than the normal removal of dead or crossing branches needs to be done. If they are shrub-types, grown for the color of the stems in winter, then I would wait to prune them until the normal time - early spring. They should have dropped their leaves by now, so the only thing the bushes would be doing now is growing roots - there are no leaves to be fed, so no reason to lessen the drain on the roots - they will just be growing more roots this year if you move them.

That said, if pruning them now will make it easier to move them, and you don't care about the show from the colored stems for the winter, then you CAN prune them now, just as you would have done if you had waited until the spring.