We do our best to bathe them every 1-2 weeks, but to be honest, we have gone beyond that at times!
We brought Wrigley home at 12 weeks and we started bathing her right away.
We always make sure we dry them all the way, especially in the cooler months.
It's not unusual for them to shake while you are giving them a bath. We bathe them in the kitchen sink, we have a deep one. We just make sure the water is warm, but not too warm.
You could look into some of the dryers that are quiet, that might help some.